Side Note: The phrase "Vancian Casting" refers to the standard rules for casting spells in PF2, where players track how many spells they can cast each day with spell slots and/or prepared spells.

Summary:

This "Mana Casting" system was made from a desire for a simple mana system that replaces the need to track the spending of spell slots to cast spells, It allows for casting using mana pools while minimizing changes to the core rules. The basic idea is that casting a spell costs mana equal to the spell level and that casters have two mana pools: A larger pool (called Mana) that is replenished once per day during daily preparations and a smaller pool (called Focus Mana) that is replenished whenever you refocus. Spell slots and prepared spells are not lost when you cast spells. You won't be able to cast as many higher level spells at once compared to using standard Vancian casting rules, but you can always cast a few spells in a pinch so long as you have time to refocus.

The simplicity of this system allows Mana casting to be swapped in to replace standard Vancian Casting at any point in a game. Likewise, both Vancian Casting and Mana Casting can be used at once by two different players in the same game.

Table: Mana Pools By Level

Explanation: The below Table shows maximum Mana and Focus Mana at each level. It's designed such that a mana caster can spend all of their mana (regular Mana and Focus Mana) in a single encounter to cast the same number of their highest level spells as a vancian caster, and can always cast at least one of their highest level spells by refocusing.

Example of mana value rationale: A level 10 Vancian Caster in PF2 has 3 level 5 spell slots that they can cast in an encounter ^{(Sorcerers are the exception with 4 spell slots of each spell level instead of 3, see 'Epic' Mana in the extra content for alternative Mana pool values that sorcerers can use}). A level 10 Mana Caster can also cast 3 level 5 spells in an encounter by spending all of their Mana (10 Mana 5 Focus Mana). Afterwards, the Vancian Caster would still have the rest of their lower level spell slots for the day while the Mana Caster would be able to recover their 5 focus Mana and be able cast any of their spells again (with less burst potential).

\You can only cast one 10th level spell each day as normal. Feats that grant a second 10th level spell slot allow you to cast a second 10th level spell each day*

Rules/Details:

Mana Pools: Spellcasting classes gain two Mana pools: Mana and Focus Mana. Mana is equal to your level and is fully replenished during daily preparations. Focus Mana is equal to half of your level (rounded up) and is fully replenished whenever you use the refocus activity.

Casting a Spell: Casting a spell expends mana equal to the spell level, drawing from Focus Mana first. Cantrips are free.

Example: A level 7 cleric has 5 Mana and 2 Focus Mana remaining. They cast a level 4 spell, expending 4 mana. This draws first from their Focus Mana, reducing it to 0, and then from their Mana, leaving them with 3 Mana and 0 Focus Mana.

Prepared Casters: Prepared casters (clerics, wizards, etc.) still prepare spells each day in their spell slots as normal. Casting a spell does not expend the prepared spell and instead expends Mana equal to the spell level. A prepared caster can continue to cast the same prepared spell so long as they have the Mana to cast it.

Spontaneous Casters: Spontaneous casters (bards, sorcerers, etc.) have a spell repertoire with their spells and signature spells as normal. Casting a spell does not expend a spell slot and instead expends Mana equal to the spell level. A spontaneous caster can continue to cast spells of a particular spell level so long as they have the Mana to do so.

Refocusing: Whenever a character uses the refocus activity to restore focus point(s), they also fully replenish their Focus Mana. They can also use the refocus activity to only replenish their Focus Mana if they would otherwise be unable to use the refocus activity. If they have more than one Focus Mana pool, such as from both a class and an archetype, they choose which Focus Mana pool to fully replenish.

Spellcasting Archetypes: If an archetype gives you spell slots, you also gain a Focus Mana pool for the archetype equal to the max spell level you can cast from the archetype. Casting a spell from the archetype expends mana from the Focus Mana pool for the archetype instead of expending the granted spell slots. You do not gain a normal Mana pool for the archetype. You can have more than one Focus Mana pool, such as from both a class and an archetype. When you use the refocus activity and have more than one Focus Mana pool, you choose which Focus Mana pool you want to be fully replenished.

Divine Mana (Cleric Only) (Replaces Divine Font): Instead of a gaining harm or heal spell slots equal to 1 their charisma modifier, Clerics gain a Divine Mana pool each day with Mana equal to their [maximum spell level] times [1 their charisma modifier]. This Divine Mana can only be used to cast harm or heal spells (whichever was chosen by the cleric) of a spell level up to their maximum spell level. Casting a harm or heal spell with Divine Mana expends Divine Mana equal to the spell level. Clerics must choose to use this Divine Mana for only harm or heal spells as normal.

Example: a level 7 cleric with 19 charisma gains a Divine Mana pool each day equal to 4(maximum spell level) x 5(charisma modifier 1) = 20. They can cast up to 4th level heal spells (or harm spells if they chose harm instead) using this Mana.

Drain Bonded Item (Wizard Only) (Free Action) (Replaces the normal Drain Bonded Item)

Traits: Arcane, Wizard

Frequency once per day

Requirements You haven't acted yet on your turn

Description: You expend the power stored in your bonded item. During your turn, you gain the ability to cast one spell you prepared today without expending Mana. You must still Cast the Spell and meet the spell’s other requirements.

Staves: Staves work the same for all casters. A caster can prepare 1 staff each day during their daily preparations, charging it with mana equal to the maximum spell level they can cast. Casting a spell with a staff expends stored mana from the staff equal to the level of the spell. A caster can instead choose to use their own mana/focus mana in place of the staffs mana to cast a spell from the staff. A caster can only cast spells from a staff with a maximum spell level equal to the highest level of spells that they can normally cast.

That's it! Below is some extra content (hidden to show it's not as important)

Custom Item: Pearl of power. (Invested) (Variable Cost)

Description: This item increases the users maximum mana in their Mana pool by the amount listed. A character cannot invest more than one pearl of power.

Cost: Equal to a wand of a spell level equal to the amount added to your Mana pool. (If it adds 4 to your Mana pool it costs the same as a wand of a 4th level spell)

Alternative Mana and Focus Mana pools:

The mana and Focus mana values I chose above may not make sense for your game. Below are some alternative values for Mana and Focus Mana to use as you see fit. They all make a caster stronger. 'Epic' has the Mana pool grow faster than level to give casters more burst potential. 'Epic' also can be more appropriate for Sorcerers then the standard mana values as it allows sorcerers to cast up to 4 max level spells at once, the same as in regular pf2 where they get more spell slots than the other classes. 'Legendary' provides the same total mana as 'Epic' but decreases Mana and increases Focus Mana to give casters more sustain. 'Mana Only' does away with Focus Mana, making casters all burst and easy to run out of spells if they only cast their highest level spells. 'Focus Mana Only' does away with normal Mana, giving casters the same total mana going into each fight after refocusing. Both Mana Only and Focus Mana Only can be hard to balance at high levels as one has too much burst and the other too much sustain. You could also ramp up the power and get rid of all the silly number values by just making both Mana and Focus Mana equal to your level :).

Potential issues:

1. Its untested! I'm not sure if the mana and focus values make sense or even the system as a whole as I have not playtested it.
2. Mana Casting was primarily made for spellcasting during combat. While out of combat a Mana Caster can repeatedly cast their highest level spells by spending 10 minutes to refocus between each cast. This can definitely give a different feel to a game when players are casting spells like teleport multiple times in a day. You may want to consider limiting certain spells to a number of uses each day if this becomes an issue.
3. At higher levels, you can cast many low level spells in an encounter, significantly more than you could with standard vancian prepared casting rules. However, you could achieve a similar number of castings of a low level spell in a vancian prepared casting system by replacing all of your spell slots with heightened versions of that low level spell, so this may not be a significant issue. Spontaneous casters can already do this using signature spells.
4. Prepared casters have more to gain from Mana Casting than spontaneous casters. Prepared casters can prepare different spells from their spell lists each day without needing to worry about losing prepared spells while spontaneous casters are only able to change their spell repertoire when they level or retrain (outside of specific feats). However, spontaneous casters still have their signature spells which help level the playing field as prepared casters still need to prepare heightened spells at each level that they want to cast them at. Any ideas for how to make this more balanced?

Any feedback or suggestions would be appreciated! Let me know if this system is too complicated/confusing, too powerful, too weak, or if there are other issues that arise from using it.