I wanted to update this great post by /u/GRFenrir, with the patches since CK3's release and the new stuff from Northern Lords. Some of the advice there is out of date, and some of it is just plain wrong. Plus, honestly? I just wanted to have my own notes all in one place.

So. Here's 47237264545 words of advice on how to min-max your reformed or custom faith.

Up front, I do want to say that most of this advice is pretty Machiavellian. The Enlightenment hasn't happened yet, and you're a (probably bloody-handed) monarch, so you're going to be ruling through a combination of naked power, wheedling, and fear. If you want to have a more humanist and tolerant approach, that's fine, I'm just gonna tell you that that's not as effective.

The first and IMO most important part of determining your playstyle are your Tenets.

EXCELLENT TENETS

As long as you can take these tenets, they should be your first picks. You can always take these tenets and you're almost never wrong to do so.

Alexandrian Catechism

• 20% Monthly Learning Lifestyle Experience
• This does one thing and that thing rules. Lifestyle experience is one of the best things you can get from a religion.

Armed Pilgrimages / Struggle and Submission

• (Armed Pilgrimages) -20% Holy War Piety Cost
• (Struggle and Submission) 50% Piety and Devotion from Holy Wars
• 25% County Conversion Speed per owned Holy Site if no Head of Faith
• Can declare Great Holy Wars if Faith has a Head of Faith
• (Armed Pilgrimages) Completing a pilgrimage grants a Monthly Piety from Knights modifier
• (Struggle and Submission) Completing a pilgrimage grants a Same faith opinion modifier
• These two nearly-identical traits are great, but work differently depending on what sort of head of faith you have (if any) and where you are in the world.
• If you have no head of faith and at least two holy sites, then this is a fantastic trait. So if you're starting as a regional or fringe religion (eg Krstjani, Cainitism, Apostolic Christianity, Coptic Christianity) and control some of the offbeat holy sites, then this can give you some real value from 50% or more conversion speed. However, this tenet is limited to Abrahamic religions (including Dualism), and most of those want heavily-contested sites in the Middle East or western Europe. Pagans really wish they could take these traits!
• If you have a temporal head of faith (which should be you, you founded the dang religion, right?), then this is an extra Kingdom-level invasion, about once or twice per ruler, and that's great. Plus, all of your vassals will pile in to help on top of their normal levy contribution. All of the lower titles are going to go to random excess children of your vassals, but as long as you're doing a good job of making sure all of your vassals are your culture, that's not a big problem.
• If you have a spiritual head of faith, this is situational. You can compete to have your choice of heir win the title from the great holy war, but it may not be a location or a time that is convenient to you. If you're unlucky, you won't even have an eligible beneficiary (an unlanded adult close relative in your dynasty who isn't currently heir to any titles). It's still helpful, since it's spreading your religion and might even result in your dynasty members getting some independent kingdoms for Dynasty of Many Crowns, but you could just do that yourself on your own timetable.

Astrology

• 25% Naval Speed
• Enables the Divine the Stars decision
• This is all about Divine the Stars. Divine the Stars is a free decision that gives you a decade-long buff, granting 25% lifestyle experience in a randomly-chosen lifestyle, as well as 2 to the corresponding attribute and -2 to an opposed attribute. Lifestyle experience is one of the strongest things you can get from a tenet. The randomness isn't ideal and makes it difficult to stack bonuses, but this is one of the few remaining unnerfed sources of extra lifestyle XP from your religion.

Esotericism

• Learning Education may also grant the Wise Man trait
• Makes Wise Man, Mystic, and Miracle Worker virtuous
• Pilgrimages have a chance to grant or upgrade the Wise Man trait (based on a learning challenge)
• (Unlisted) Removes all of the negative results from the Mystical Communion except Illness
• Wise Man gives you access to the Mystical Communion decision, which turns 100 Piety into 300 Learning XP. (Don't bother doing Mystical Communion when you're not doing a Learning lifestyle, it's a waste of Piety.) Normally, this decision comes with the risk of annoying other characters or lowering a level of devotion, but this tenet removes all of those bad events! Doing a pilgrimage is already worth it for the Pilgrim or Hajji trait, and this usually gives you Wise Man unless your piety is very low, so it's learning XP and a good chance at general opinion and monthly piety. Just a great all-rounder trait.

Mendicant Preachers

• 33% County Conversion Speed
• Completing a pilgrimage grants a Holy Order Hire Cost modifier
• Makes Temperate a virtue
• Makes Gluttonous a sin
• That's a lot of conversion speed! It's not as much as Armed Pilgrimages / Struggle and Submission, but those are only available to Abrahamic religions, only give conversion speed if you don't have a head of faith, and even then, you need to control holy sites to get that bonus. This tenet is always useful, no matter what religion you are, no matter where you're playing.

Warmonger

• Members of the clergy can serve as Commanders or Knights
• Grants the Conquest Casus Belli
• Grants the Invasion Casus Belli once per lifetime
• No Offensive War Opinion
• Being at peace for more than 6 months lowers Vassal Opinion and Popular Opinion
• Can declare Great Holy Wars if Faith has a Head of Faith and is Organized
• (Unlisted, Norse only) Knights that are neither Calm nor Craven can become Berserkers
• The Conquest and Invasion Casus Belli are huge and Feudal governments don't usually get them. If you want to conquer the world, Conquest helps a lot. Even if you have the Conquest CBs, getting rid of the Offensive War opinion penalties is very handy. Negating those opinion penalties would be a pretty decent tenet on its own, even if they weren't bundled with some of the best CBs in the entire game.
• If you have a head of faith, the Great Holy Wars work like Armed Pilgrimages / Struggle and Submission, above. It's pretty much an extra Kingdom-level invasion once or twice per character with a temporal head. (Spiritual heads are kinda bad, tbh.) Warmonger is basically two top-tier traits and one passable one, all wrapped up into one great package.
• There's no reason to take both Warmonger and Pursuit of Power. The only reason Pursuit of Power is worth considering at all is because Warmonger is only available to non-Abrahamics (except for a couple of Muslim faiths that start with it). Those Muslim faiths should definitely keep Warmonger and skip Struggle and Submission, unless you have no head of faith.

SITUATIONAL TENETS

These tenets are strong, but have some sort of fundamental limitation in how they can be used or when they're useful. These tenets narrow what you're good at, or only come into their own when stacked with other bonuses.

Communion

• Enables the Seek Indulgences interaction with the Head of Faith
• Spiritual Head of Faith can Excommunicate characters
• Makes Honest a virtue
• Makes Deceitful a sin
• Makes Excommunicated a crime
• This is actually two different tenets in one, depending on what sort of head of faith you have.
• If you are the temporal head of faith, indulgences will funnel money into your pockets, making this one of the best tenets in the entire game. This is one of the two best money-making strategies for a custom faith. The only limitation is that there's another, incompatible money-making option that doesn't require a tenet at all, and it gets incredibly clicky as your realm gets larger.
• With a spiritual head of faith, this just allows your head of faith to excommunicate characters. This is a slightly-weaker alternate version of Religious Law/Fatwa/Halakha, below (bumping it down to Marginal). You have to suck up to your head of faith to excommunicate, but you'll generally have some luck trying to excommunicate murderers and lechers as well as characters with sinful personality traits. You can also turn excess gold into piety, but there are better tenets for piety if that's what you're concerned about. It only comes up rarely, but your head of faith can also remove Infamy traits from you, which is handy if your heir gets up to some nonsense before you take over.

Ecclesiarchy / Pentarchy

• 0.1 Monthly Fervor per Holy Site
• Completing a pilgrimage grants a Clergy Opinion modifier
• Fervor is actually pretty annoying to come by once your religion gets really big, and this is a consistent trickle to make sure it never gets too low. The only downside is that fervor only really matters once you get really big, at which point there's nobody who can stop you from doing whatever you want anyway.

Human Sacrifice and Gruesome Festivals / Blot

• Executing prisoners grants Piety. 25 for unlanded characters, and 50-500 for landed characters based on their highest title
• (Unlisted) Sacrificing a head of faith makes that faith significantly more likely to target your kingdom for a Great Holy War
• (Human Sacrifice) Grants the Raid for Captives Casus Belli
• (Gruesome Festivals / Blot) Enables the Hold Grand Blot decision
• This is one of the strongest ways to stack up a lot of piety. But Fundamentalist also gives piety for executing different-faith prisoners, and if I carefully manage how many prisoners I have, that's more than enough to unlock or pay for Holy Wars in my experience. I haven't yet found a use for an excessive amount of piety after I've already founded a custom faith, but maybe someone out there has an idea.
• Gruesome Festivals are better than Human Sacrifice. The captives CB is totally useless (unless you want to capture and sacrifice the Pope as a meme strategy); just declare a Holy War and siege more castles than is strictly necessary. You'll get tons of captives. Blots aren't anything special; you're pretty much just trading some prestige for a some piety, with a bit of vassal opinion on the side. That's handy for getting a new ruler established. The only reason to use Human Sacrifice is if you don't have the DLC.

Legalism

• -10% Law Cost per Virtue trait (up to −30%)
• 10% Law Cost per Sin trait
• Characters are less likely to join Factions if the Liege has a virtue trait
• Characters are more likely to join Factions if the Liege has a sin trait
• Electors are more likely to vote for the Liege's choice if it has the Just trait
• Makes Just a virtue (x2)
• Makes Arbitrary a sin (x2)
• Very strong if you are using elective succession and are good at managing your heirs' education. Very dangerous otherwise. The law cost is unimportant; all that matters here is easing elective succession and strengthening transitions to a new ruler. If you're not using elective succession, don't bother with this, because Legalism makes the occasional transition to a bad heir so, so much more punishing. Be careful with this one, it will blow your empire straight to hell if you're not very picky about your heir.

Pursuit of Power

• -50% Title Creation Cost
• -50% Tyranny Gain
• -10 Direct Vassal Opinion
• Grants the Conquest Casus Belli
• Grants the Invasion Casus Belli once per lifetime
• Makes Ambitious a virtue
• Makes Content a sin
• This is the Christian version of Warmonger. Like with Warmonger, the Conquest and Invasion Casus Belli are huge and Feudals don't get them. If you want to conquer the world, Conquest helps a whole lot.
• The rest of this is just gravy. The tyranny reduction looks tempting but it's usually more than offset by the -10 to all vassals. The title creation cost reduction is nice, but you can usually leave that up to your vassals for most titles.
• This is only useful to Christians, Jews, and Dualists, or the occasional Feudal Muslim. Muslims are almost always Clans, so they get the main benefit of this tenet already. Eastern and Pagan religions can and should take Warmonger instead. The reason you don't want Pursuit of Power if you already have the Conquest CBs is because it makes your vassals less happy to be ruled, and I believe applies a personality modifier that makes them more obnoxious. (That might just be the result of having more Ambitious vassals running around, though.)

Sacred Lies

• 50 Piety when successfully completing a Scheme
• 20 Agent Acceptance
• Makes Deceitful a virtue
• Makes Honest a sin
• This supercharges your schemes, and also encourages your courtiers to get into their own schemes. This not only means you're better at your own skullduggery, but there are lots more hooks to exploit. It also does mean there are a lot more murders, so watch out for that. The piety is negligible unless you're just constantly spamming seduction and hostile schemes. (You don't get piety for Befriend, Romance, or Sway.) If you just want all intrigue all the time, this is your go-to.

Tax Nonbelievers / Jizya

• 20% Domain Taxes if different faith
• 25% Levy Reinforcement Rate if same faith
• -25% Levy Reinforcement Rate if different faith
• The levy reinforcement modifiers are nothing. (Levies are rarely important.) You are here for 20% domain taxes, which is huge. But it comes at the cost of not converting your provinces. That's a significant pain, and means eating popular opinion penalties (and thus periodic peasant revolts) pretty much forever unless you negate or offset those penalties somehow. Most of the options to do that either involve heavy investment (a perk deep in Stewardship lifestyle's middle tree) or come with significant annoyances of their own (Pluralism doctrine or a Syncretism tenet). You can just crush the peasants every so often, that's definitely an option.
• If you can find (or set up) a juicy capital duchy that considers your religion only Astray (or even Righteous), that's one way to get big value out of this. Different Eastern religions, different Pagan religions, or Muslims with the same succession doctrine are all options. Ruling over different-religion provinces where the local religion has with Gnosticism or Pastoral Isolation as a fellow Gnostic or Christian is also an option, but these religions are rare and probably will not spread if you're not the one spreading them.
• Your vassals will convert their provinces normally. That means losing the 20% tax from them as they do that, but if you're minmaxing properly, the bulk of your income should be coming from your domain anyhow.

MARGINAL TENETS

These tenets contribute relatively little overall. They're replacement-level options, either doing something that isn't useful or just not doing much at all.

Adorcism

• Enables the Seek Aid of the Spirits decision
• Makes Possessed a virtue (x2)
• This is for people who want the clicky decision spam of CK2's secret societies back. Seek Aid of the Spirits is a 5y-cooldown decision that takes scaling gold and gives you a low chance for a great permanent trait, a decent chance for a very long-lasting temporary positive trait (eg 3 Martial and 4 Prowess for 20 years), a decent chance of nothing, and a small chance of Possessed, Infirm, or Ill. I found that the risk of a bad event was fairly low - lower than the chance of getting sick on a Pilgrimage in my experience - and mostly seemed to favor Possessed. The benefits aren't large, cost gold, and are mostly limited to your character, so this isn't great, but if you really want more clicky stuff don't worry too much about the risk of negative traits. Just avoid Cynical, low-learning chaplains, and don't skip the offering of gold.

Ancestor Worship

• 100% Prestige from Level of Splendor
• 5 Close Family Opinion
• 50% Maximum Long Reign Opinion Bonus
• Completing a pilgrimage grants Close Family Opinion modifier
• This gives you a boost to initial prestige to get over the hump to unlock better Conquest CBs on each new ruler. The rest is a potpourri of stuff you'll never notice. Not strong but occasionally handy.

Aniconism

• -33% Temple Holding and Temple Building Construction Cost
• -33% Temple Holding and Temple Building Construction Time
• This helps you get set up faster if you're going spiritual/no head of faith, and makes those temples you're building build up faster. This is probably not a trait you want after making a new faith, since you may have spammed temples everywhere useful to get enough piety to form the faith, but if you start as one of the Christian heresies with this tenet, you can get some mileage out of it before reforming to something stronger.

Auspicious Birthright

• 5% Chance a child is born with the Miracle Worker trait
• Makes Miracle Worker a virtue (x5)
• (Unlisted) Removes all of the negative results from the Mystical Communion except Illness
• This is a weaker, less controllable version of Esotericism. If you've got ridiculously good control over who your heir is and a ton of stacked Fertility, this might be good for a meme.

Bhakti / Patron Gods

• Enables the Determine Bhakti decision
• This was nerfed a while back, making it a replacement-level option for most faiths, including all custom faiths. So, while it is very strong for for Vaishnavism only, it is not a strong option for Smartism, Norse, or any sort of custom faith.
• Vaishnavists only - not even custom faiths based on Vaishnavists - can take Lakishmi, for 10% domain taxes and 20% stewardship experience. That's a huge benefit, and makes Vaishnavism one of the few historical religions that can hang with a minmaxed custom religion. (It's pluralist, though, that kinda sucks.) The other patrons aren't great, but you don't have to use them.
• For custom Eastern faiths or non-custom Smartists, the best you're getting out of this is 5% domain taxes from Kubera. That's pretty cool, but limited by the fact that unlike most domain tax bonuses, it's not increasing the taxes your vassals pay to you (because most of them will not take this patron). Smartists can get 10 vassal opinion instead, to smooth over new ruler transitions.
• For Norse (which is only available with the DLC), it's all situational options. Odin can be a lot of piety if you're executing prisoners regularly. Ullr's pretty cool for reducing army micro. Freyr is less micro to deal with provincial control.
• Don't be fooled by the wiki. It says Shaivists can choose Dakshinamoorthy, for an eye-watering 20% Monthly Lifestyle Experience Gain, but Shaivism doesn't actually get the Bhakti tenet or the Determine Bhakti decision. A custom faith based on Shaivism gets the boring list with no lifestyle XP. I'm not sure if this was a nerf to an OP tenet/faith, or just a more respectful way of representing the beliefs of actual Shaivists, but either way you can't cheese this any more.

Carnal Exaltation

• 25% Fertility
• Makes Lustful a virtue
• Makes Chaste a sin
• This gives you lots of children. Having lots of children can be more of a downside than an upside, though, as it forces you out of Partition-based succession or forces you to spam Disinherit. What does make it useful is that it ramps up your courtiers' tendency to get into affairs. This makes seduction easier, and you can make adultery or homosexuality illegal for lots of hooks. However, your heirs will often get into trouble before you take control of them. This generally makes the game more chaotic in a low-impact way, but it can be useful if you're mainly using bastardy to control who inherits.

Divine Marriage

• 10 Vassal Opinion if married to a Close Family member
• 500 Piety if first marriage is with a Close Family member and Monogamous
• Marry your mother or an aunt or something, as long as she's over 45, and get your children from polygamy, concubinage, or extramarital affairs. Inbreeding without going deep into the Blood dynastic legacy is a terrible idea but this doesn't require (or reward) inbreeding anyway. It's a small benefit for a small amount of micromanagement. This will lead to a lot more inbred NPCs, though.

Gnosticism

• 2 Learning
• -2 Stewardship
• -5 Stress when granting a County Title, -15 Stress when granting a Duchy Title, -65 Stress when granting a Kingdom Title, and -160 Stress when granting an Empire Title
• Faiths with the same tenet are considered Righteous
• Makes Temperate a virtue
• Makes Gluttonous a sin
• This turns holy wars into stress dumps, which is kinda nice as stress dumping goes, but managing stress isn't something you usually need from your tenets. The weird part is that it means other religions (Dualist religions and a handful of Abrahamic heresies, most notably Catharism, Bogomolism, and Druze) count as righteous. These are too rare to make much difference, though. Other than that, this is basically a nothing tenet.

Hedonistic

• 100 Piety when holding a Feast
• 20% Stress Loss
• Makes Gluttonous a virtue (x2)
• Makes Temperate a sin (x2)
• Weaker than Ritual Celebrations, but stacks. Worth about ~1.7 piety per month if you spam feasts on cooldown.

Literalism

• Enables the Literalist Debate interaction with characters of the same faith
• Makes Scholar a virtue
• Makes Astute Intellectual a virtue
• Makes Mastermind Philosopher a virtue
• The main use for this is some very easy, very controllable virtues. Those are very handy, and get even more useful if you have other tenets based on virtues or sins (like Legalism). The Literalist Debate interaction is pretty close to useless, though; it gambles piety with one of your vassals, with winning weighted to higher learning, more virtues, and fewer sins. It's not reliable, especially compared to something like Ritual Celebrations.

Monasticism

• Enables the Ask to Take Vows interaction with Courtiers
• Makes Temperate a virtue
• Makes Gluttonous a sin
• This does almost nothing. There are sizable penalties to trying to convince any character that is actually in a line of succession to take the vows, so large that you'll probably never be able to use this to manage succession. You can imprison characters and force them to take the vows, but you could just execute them at that point. Monks do still inherit claims. Monastic vows don't annoy their relatives (or trigger Kinslayer, but you turned that off, right?) but that's a very weak benefit for a tenet.

Polyamory

• No opinion penalties from extramarital relationships
• This simply makes affairs not annoy your spouse or their relatives. Does absolutely nothing unless you have terrible Intrigue and care a lot about your spouse's or spouse's family's opinion. Possibly useful if you're using Divine Marriage, marrying your mom or an aunt, then relying on bastardy to pick your heirs? Even then, meh. This also locks you into a fairly libertine society.

Religious Law / Fatwa / Halakha

• -10% Law Cost
• Enables the Temporal Condemnation interaction with Vassals
• Temporal Condemnation requires 14 learning (although spouse assistance counts) and 100 piety, has a five-year cooldown, and only works on someone with a sinful personality trait. (It doesn't work on Infamy traits.) It gives them as a small opinion penalty, but, more importantly, it's a crime you can punish with title revocation. This isn't very useful. You can just have your chaplain make a claim on one of their counties. Usually they'll revolt anyway, which lets you strip their titles while they're in prison. This might be useful if it were an imprisonment reason, since it would allow stripping more titles without revolts or even manage your heirs, but as it is, it doesn't give much value.

Ritual Celebrations

• 5 Vassal and Courtier Opinion
• 100 Piety when holding a Feast
• −100 Piety when refusing to attend a Feast
• The baseline replacement-level tenet. Gives ~1.7 piety a month if you're spamming those feasts, and a little bit of vassal opinion. There's no downside to taking this, it's just free bonuses, but you can certainly pick something stronger.

Ritual Hospitality / Puja

• 0.3 Monthly piety per powerful vassal on the council
• Enables the Host as Honored Guest interaction with landed characters
• Makes Generous a virtue
• Makes Callous a sin
• Generally weaker than Ritual Celebrations for piety. Host as Honored Guest lets you spend 100 piety to gain usually about 20 opinion with a landed character of a friendly religion, on a one-year cooldown. That's handy? I guess? But Sway is free.

Ritual Suicide / Consolamentum

• −50% Short Reign Duration
• Enables the Initiate Endura / Initiate Consolamentum decision
• Suicide is not terribly useful. But this is 10 vassal opinion at the time when vassal opinion most matters, ticking down over time. That's handy. Generally more useful if you're staying Tribal, trying to hold together a multicultural/pluralistic empire, or somehow managed to become a non-Muslim Clan.

Sacred Childbirth / Kudikis Lemti

• 10% Fertility
• -50% Pregnancy Complication Chance
• Fertility is not usually a useful bonus, and pregnancy complications are fairly rare. This is slightly more useful with a matriarchal society, but even then, meh.

Sky Burials

• Enables the Give your Ancestor a Sky Burial decision
• Small Disease Resistance (Health) Boost
• This is all about the Sky Burial decision. It's once per ruler, but it gives a sizable vassal opinion bonus and some starter piety to start unlocking Holy War CBs again. It's a better version of Ritual Suicide, above, and like that tenet, it's mainly useful for very difficult ruler transitions, such as when staying Tribal, holding together a large and diverse empire, or as a non-Muslim Clan.

Sun Worship

• -25% Attrition in Desert and Desert Mountains terrain
• Enables the Sun Trial interaction with Prisoners
• 250 Piety when holding a Feast in May, June or July
• This is ~4.2 piety a month if you spam those feasts at the right time. That is a whole lot of piety. Everything else about this is chaff. The attrition modifier isn't noticeable, and Sun Trials? Woof, Sun Trials. You can only put a person on Sun Trial if they are a criminal in your prison. You get 75 piety, and there's about a 50/50 chance that they die. If they don't die, you can murder them while they're helpless, and it's an Intrigue challenge to not get caught. If they survive, they get away scot-free (and the crimes are forgiven) and they're pissed at you. Sun Trials are less useful than just executing people (especially if you have Human Sacrifice and/or Fundamentalism), but, honestly, why would you not take this tenet if you're going out of the way to revive Zunism?

Unrelenting Faith

• 4 Prowess
• 2 Faith Hostility Advantage
• Members of the clergy can serve as Commanders or Knights
• 2 advantage on every fight ever and 4 prowess to all of your characters and all of your knights? That's a small but generally-useful bonus. Clergy serving as commanders or knights only makes a difference if you have Theocratic clergy, and even then it's not significant.

SABOTAGE TENETS

These tenets come with some sort of nasty drawback, or do nothing whatsoever. Some of them are amusing, or marginally useful as part of a combo, but generally you want to avoid these.

Adaptive

• 30% County Conversion Resistance
• 15 Different Faith Liege Opinion
• 15 Opinion of Different Faith Liege
• −25% Different Faith Popular Opinion
• Different faith vassals are less likely to join Independence and Populist factions
• You should remove or convert different-faith vassals as quickly as possible unless you are specifically roleplaying religious tolerance. Some people have proposed running this with Tax Nonbelievers/Jizya, but that only affects domain taxes (from your personal holdings), not taxes paid by your (different-religion) vassals. Unless you have different-religion vassals or are regularly losing religious wars, this only gives you a tiny boost to popular opinion (less than 5 in most cases) in different-religion provinces, which isn't enough to make an impact. Adaptive doesn't inherently make you weaker, but attempting to make use of it does.

Asceticism and Inner Journey

• Enables the Meditate in Seclusion decision
• (Asceticism) Makes Temperate virtuous
• (Asceticism) Makes Gluttonous and Greedy sinful
• (Asceticism) Makes Eager Reveler, Famous Reveler and Legendary Reveler sinful
• (Inner Journey) Makes Patient a virtue
• (Inner Journey) Makes Impatient a sin
• These are both basically the same tenet (and thus should not be stacked.) Meditate in Seclusion is a free, relatively-short-cooldown way to burn off a little bit of stress. (You get better at meditating the more you do it successfully. Your castle always burns 10 stress, safe ourdoors usually burn 20 but can ding you for 20, and harsh outdoors can burn up to 40 but will usually ding you for 20 without some practice.) That's not especially useful. If you make sure to spam it on cooldown, relatively late in your life you can flip one of your usually-sinful traits, chosen at random, to a usually-virtuous one by meditating outdoors. That might be useful, but it can also mean losing useful traits like Greedy or Ambitious, or picking up annoying traits like Generous. It also doesn't take into account the actual sins or virtues of your religion, so you might pick up a sinful trait if you have Sacred Lies, Hedonistic, or Carnal Exaltation. This trait-flipping generally doesn't come until after many attempts, so it's not terribly impactful.
• Asceticism cuts you off from spamming Feasts, and Inner Journey makes one of the least-bad "negative" traits from the bad childhood events into a sin, so both of these tenets just suck. The only reason I'd ever use them is for stacking up lots of sinful traits to abuse Religious Law/Fatwa/Halakha, but that's a very weak benefit.

Communal Identity

• 10 Same faith opinion
• 50% Culture Promotion Speed if same faith
• 50% County Conversion Speed if same culture
• -50% County Conversion Speed if different culture
• This is a trap. That -50% conversion speed penalty is on all the time after the early game. After the early game, you need your vassals to do most of the converting. However, your vassals don't understand this tenet, so it will reduce their conversion speed to a crawl. The only way to make use of this is to tediously match your vassals' culture to their provinces' culture, but that comes with non-matching culture penalties, making it a different kind of trap. It does also come with that tempting culture conversion speed, but you lose more time on the faith conversion if you're doing that first. The 10 same faith opinion is the only meaningful bonus here, and there are better ways to get opinion bonuses.

Dharmic Pacifism and Pacifism

• 1 Domain Limit
• 10 Opinion of other Pacifists
• (Dharmic Pacifism) 20% County Conversion Resistance
• Cannot declare Holy Wars or Raid
• (Pacifism) Rulers at peace for at least two years will have their Piety change by 1 each month
• Makes Calm a virtue
• Makes Wrathful a sin
• If there was a tenet that added Holy Wars and did nothing else, it would be one of the best tenets in the game. Domain limit bonuses and faith opinion bonuses are both handy, but one of the main benefits of making your own religion is having a free Holy War CB on the entire world. Giving that up is playing the game on intentional hard mode. If you absolutely must take this, Taoism can double up on both pacifist tenets to double most of the benefits.

Natural Primitivism

• 25% Stress Loss
• -25% Stress Gain
• 50% Law Cost
• 100% Tyranny Gain
• Characters don't wear clothes if the nudity game setting is enabled
• Meme tenet for the pervs out there. Increasing tyranny sucks so bad, and the benefits are negligible. It also locks you into a libertine society.

Pastoral Isolation

• 10 Different Faith Liege Opinion
• 30% County Conversion Resistance
• -10% Monthly Development
• 20 Enemy Demand Conversion Acceptance
• Christian Faiths are considered Righteous
• Counties and characters may sometimes reconvert to this faith
• This does absolutely nothing except sabotage your development. The vast majority of this tenet is useless garbage that only kicks in if your territory gets conquered by an enemy and stays that way. How often are you letting that happen? The stuff about considering other Christians righteous looks interesting, but is useless, since they still think you're Astray; it's your religion that likes them, which is not useful. This one just plain sucks.

Reincarnation

• 20% County Conversion Resistance
• 4% Chance of a child to gain the Reincarnation trait and an ancestor's personality trait at age 9
• This does nothing. The Reincarnation trait is too rare and too weak to matter, and getting a random personality trait may or may not be useful. This is a blank tenet.

Ritual Cannibalism

• Cannibal is no longer Criminal
• Makes Cannibal a virtue (x2)
• I've only ever seen a Cannibal event fire twice ever, and neither time was when I had this tenet. If this tenet makes those events more common, I didn't notice it. Totally useless.

Sanctity of Nature

• 5 Popular Opinion
• 5 Advantage and -25% Attrition in Forest, Jungle and Taiga terrain
• 10% Building Construction Gold Cost
• Most of the map is not forest, jungle, or taiga, and the bonus in those territory types is not large; contrast with Unrelenting Faith, which is always on. 5 popular opinion is never enough to make a real difference. This would not be worth it even if it didn't have the building cost increase, but it does, so this is just terrible.

Sanctioned False Conversions / Taqiya

• 30% County Conversion Resistance
• Counties and characters may sometimes reconvert to this faith
• Does nothing. It doesn't even kick in unless your territory is conquered, and even then, you can just convert it back when you reconquer it. Weird that Christians can't take this, especially since you'd be making some sort of regional heresy. Regional heretics did sometimes pretend to be good Catholics. Whatever, nobody wants this chaff anyway.

Vows of Poverty

• Enables the Take Vow of Poverty decision
• Makes Generous a virtue (x2)
• Makes Greedy a sin (x2)
• Vows of Poverty are -20% income for 2 piety a month. Compare this with Ritual Celebrations, which is just better. You don't have to take a vow, but what's the point of this tenet if you don't? Useless.

All Syncretism tenets

• Members of the syncretized religion consider your faith Hostile at worst
• You consider members of the syncretized religion at Hostile at worst
• You have no opinion penalties with members of the syncretized religion, and vice versa
• Makes one personality trait virtuous, and one or two traits sinful
• This gives a bonus to diplomacy with your neighbors, but only neighbors of a specific religious group (which can't be your own). How often is that useful? It also means you can't revoke the titles of members of that religious group for free unless you are Fundamentalist, which is a pretty big pain. It does make members of that religion more copacetic with being ruled by you, but that's not really that useful, since you really want to your vassals to actually be your religion.
• Big shout out to Eastern Syncretism for being the worst trait in the entire game, because Eastern religions don't consider other religions Evil and don't have opinion penalties for other religions.

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