Hello, I'm one of you guys that prepared a Zekus thinking that magic would be enough for quite a long time... We were wrong. So, after watching around 3hours of different LC videos about the collab, there is what I learned so far that we should get ready for the final boss.

First of all, Magic is HORRIBLE for this boss, not only it is resisted by 75 but it's also countered by the boss with a thunder skill that basically nukes all units in the map for around 7k HP, this means that all mages should have their magics unequipped and that Popoi by definition is not useful in the fight.

Other interesting aspect of the boss basic passive stuff is that it casts Dark, light, fire and thunder skills and that it is God type.

Shin is basically the best unit to prepare for this fight, followed by Sevia and Robin (just because he is neutral Phy DPS) and of course Randi when released, Randi is the best by a LONG shot but not OP enough to consider Shin useless. Sevia is quite strong too, she only has one elemental Skill, so the rest of her kit is useful and her special is quite important.

Mostly people clear this fight by using a composition of 2 Physical Dpsers, one Healer/Buffer and a Physical Support. That means that in an Ideal world you would use Randi Shin, Any Healer and Sevia/Prim (Yes Prim).

The how and why:

For Physical Dpsers, they mostly use 3 Arks: one with a pink tree that we still didn't get, so no point in explaining it, The Skyship and God Slayer Ark. The reason for this is that those 2 Arks, give 20-25% damage reduction to the damage dealers while boosting Damage in the same scenario (Skyship by 25% on neutral element attack and the God slayer ark when hit with a light attack, which is common in the fight). If using, Shin, you only need Crit Phaser (the all team Crit buff), some use Auto regen and ANYTHING that boosts Phy DPS, like Crit, sTR or Impact skills. For Randi, Kaito and Sevia, they need to lear the God Slayer/killer skills and damage boosting ones, Randi has a huge adventage here because he has a heal that works quite fine for 30MP that heals around 2k,

The healer uses the March of saint SSR Ark (the one that negates cancellation of magic when using healing spells) and has Grand Regeneration, Grand Protection (most of the important damage in the fight is physical), some heal and cure all, some also cast Str or Mag debuff on the boss, but never both, I think it is because it also could activate the anti magic counter if done too much.

The physical helper is basically there to reduce damage, Sevia is quite self explanatory, she needs Dual Weild to cast her special faster and she could use the STR/Int debuff on the boss. Prim is actually quite powerful in this fight, she has a special ability that prolongs buffs and debuffs she casts by 25%, this combined with the Ark that was released with Lukiel, gives an auto regen buff that lasts most of the fight, she also can block all physical DPS with her special, so using DW on her to spam her special faster could be an option too. The physical support uses mostly 2 Arks: The Sacred Tree from the SoM collab (for the 25%HP boost, also Randi and Shin could also use this on the main slot but they lose the other reductions of damage) and Ark that was released with Lukiel..

The fight itself is quite simple, you first get hit by an AoE physical fire skill, then by a neutral physical one that you can't evade, then fight the boss and there seems to be some kind of DPS check, after some time, the boss will leave and deal additional extra physical damage, most people heal when boss leaves, then boss does damage, then people heal AGAIN (with Grand regen this time) and then the fight repeats, fire physical AoE, Neutral Physical AoE, Fire magic, Dark, Light and sometimes thunder.

I hope this helps people that don't know what get ready for the fight. Basically if you have Shin, prepare him with crit buff and skyship. If using Sevia or Robin, Learn the skills form the God Slayer Ark, and use it too if needed. Prepare a Healer for Grand Regen, Heal, Grand Protection and STR debuff. If you don't want to provide 2 main Physical DPsers, you can use Sevia or Prim to boost the stats of your main DPS and a friends DPS.

There is also a 3 bosses version of this fight but it is only 10 stars vs the 13 of the last one, The bosses in there are a slime(thunder skills), an undead (dark skills) and the God type final boss but weaker (and doesn't punish magic).

Also, the "lowest" possible average party level was around lvl 60 with 3 awakenings. But there is also, Sevia, Randi and Prim solos, the reason for them is that all of them have some for of healing, or damage reduction, this is why Shin as solo is weaker. For thos solos, usually they were lvl 90-100 and had around 55 skill points with maxed God Slayer ark.

Edit: I forgot to mention that all SoM units get 2x AP and ExP, so they are easy to prepare and that the story is VEEEEEEEEEEEEERY long, so there is a good amount of crysts. Also, the point rewards are capped at 600k and give 5 star mats like dragon eye (only one), the shop has clusters (only 1 Iirc) and some special equips, there is one that when combined with a ring, turns the unit into "Beast" type, which means that the unit can be boosted by the dog fiend unit that boosts atk by 50%, that is quite useful on Randi to nuke waves and also to activate the SoM tree SSR ability that needs to have 1 man, woman and beast type unit in the party.