BBEG "God" Help (Custom Pantheon)

[Gamereaper]

Ok, so I have a very powerful BBEG that utilizes powerful magic. I'm wondering at what level a party of 10-12 can handle this powerful being. He is an ancient being that has power on tier with gods (no divine rank). He is treated as undead when favorable, equal to 50D12 HD, full casting in arcane and divine, manifesting, and invocation progression. He's pretty much going to be a punching bag that dishes out tons of damage or near TPK every round. The party will have the aid of a small army at their disposal.

The fight will be in several phases including a part in the battle where he is inhabiting a large zombie like creature before the "real fight" begins. He created a spell that allows a contingent True Resurrection spell to be cast, it does not count towards other contingent spells. He'll also have a contingent Heal spell available as well as a few other things that total his HP around the 4,500+ mark throughout all the phases.

Around what level do you think would be appropriate to resolve this final battle?

By the way, this party is an average party. Like Monks are awesome average. They don't know how to metagame or powergame, they receive any optimization help through me and I'm mediocre at best.

If you need any of his particular tactics, let me know.

[ExLibrisMortis]

Having double full casting, invocations and manifesting won't make much of a difference compared to a cleric 50. Your players will never see the character sheet. It doesn't matter to them that the BBEG has twenty first-level spell slots. They will only see the ninth-level spell that incinerates the fighter. So think about the abilities you want your BBEG to use, that will make your players remember the fight.

With 50 HD and full casting, the BBEG can kill the entire party more than once per round just using blasphemy and minor action economy tricks (Twin Spell works, for example, even without cost reducers). Level 50 casters can use epic spells to do much more than that, but that's a sort of baseline: anything 40 HD and less just gets insta-snuffed (except that silence still works, but this is a 50 HD epic multi-caster - they can probably find a way to remove the [sonic] tag).

When fighting a party of 10-12 people, the main problem you have is that they get to do more. You can counterspell with 100% success, but if there are 12 people casting, that means 11 spells get through. That army makes it worse: a team of dragonfire inspiration bards can turn that army into a dangerous damage machine. You need to find a way to get more actions.

The best way to do it is to split the BBEG up into multiple bosses, which share one consciousness. Instead of one 50 HD BBEG, put four 20 HD bosses. That way, your players can take down one body to weaken the boss, and the boss can take four actions per round, instead of just one. Each individual body is weaker, so the party has a chance to affect it with spells, but there are more complex things to keep track of - the boss can flank, or try to heal one of its bodies, or protect one body while it casts a dangerous two-round casting time spell (which the party must interrupt).

tl;dr Epic casting makes it impossible to tell, but say 41.

[Gamereaper]

Having double full casting, invocations and manifesting won't make much of a difference compared to a cleric 50. Your players will never see the character sheet. It doesn't matter to them that the BBEG has twenty first-level spell slots. They will only see the ninth-level spell that incinerates the fighter. So think about the abilities you want your BBEG to use, that will make your players remember the fight.

With 50 HD and full casting, the BBEG can kill the entire party more than once per round just using blasphemy and minor action economy tricks (Twin Spell works, for example, even without cost reducers). Level 50 casters can use epic spells to do much more than that, but that's a sort of baseline: anything 40 HD and less just gets insta-snuffed (except that silence still works, but this is a 50 HD epic multi-caster - they can probably find a way to remove the [sonic] tag).

When fighting a party of 10-12 people, the main problem you have is that they get to do more. You can counterspell with 100% success, but if there are 12 people casting, that means 11 spells get through. That army makes it worse: a team of dragonfire inspiration bards can turn that army into a dangerous damage machine. You need to find a way to get more actions.

The best way to do it is to split the BBEG up into multiple bosses, which share one consciousness. Instead of one 50 HD BBEG, put four 20 HD bosses. That way, your players can take down one body to weaken the boss, and the boss can take four actions per round, instead of just one. Each individual body is weaker, so the party has a chance to affect it with spells, but there are more complex things to keep track of - the boss can flank, or try to heal one of its bodies, or protect one body while it casts a dangerous two-round casting time spell (which the party must interrupt).

tl;dr Epic casting makes it impossible to tell, but say 41.

Blasphemy would be far too harsh. His double casting favors the Arcane side though. There are a few things I had in mind.

End to Strife would be great to use on the Nonlethal variant since there is no penalty to him. The army won't have much of a chance either.

Action economy is definitely against his side, but I don't even know how to do action economy tricks.

The army is a simple mostly mundane army and a few core spell blasters, nothing special.

It's kind of funny that you mentioned that he needs multiple consciouses. He's wearing a colossal zombie as a skin, then he reverts to his "base form" he has contingent heals and resurrections, a couple other spells that resurrect him (pacts), followed by a clone that is everything he is at a level lower, followed finally by a fraction of his conscious being planted in the astral plane, which they must find before he reforms his body again or the process starts anew.

Oh, the Epic Spellcasting is mostly unused. He has only enough slots to cast a spell up to 9th level, the rest of the epic spell slots are used to create these powerful minions from corpses.

[noob]

True reaction of a smart BBEG:
1:Teleport to another dimension then wait the next day to have prepared the good set of epic buffing spells and many time stops and other cool level 9 spells
2:Scry the team then teleport as a shapechanged dire tortoise and get two simple actions before the fight starts then shapechange as that intangible wisp who had immunity to magic(except magic projectile and maze) and as he have a shield he does not care about those magic projectiles then he gets initiative and have yet one other round to blast that team and to trigger a contingent teleportation.
Restart this frequently until the adventurer team and the army does not have any resources.
Simply know that being level 20 gives you loads of actions on the first round(and that without even using time stop with that spell it simply gets ridiculous)