Pathfinder 1E Writing a module with a boss fight for 20th level PCs. Trying to get a handle on what PCs can do.

[RangerWickett]

So I'll admit, I've never run Pathfinder at 20th level. It's crazygonuts.

I'm working up a final boss fight, and while I'm going to integrate a lot of leeway for the GM to adjust things on the fly based on the party's composition and style, I want a good baseline. If you've ever played a PC to 20th level, or just designed a 20th level PC, could you post some details here for me?

I'm trying to figure out if the guidelines on Monster Creation (http://www.d20pfsrd.com/bestiary/rules-for-monsters/monster-creation) actually hold up in practice. I have a boss enemy with 42 AC, +34 attack bonus, and a damage output of 120 if everything hits. He has lower than expected HP, but has allied clerics healing him and dispelling debuffs, plus some allied monsters and a bard inspiring everyone. I'm unsure whether I've minmaxed my side too much, or if I'm totally wrong, and I've vastly underestimated the power of a party of 20th level PCs.

Anyone have advice?

 

[gamerprinter]

Rite Publishing Coloseum Morpheuon is a setting and 15 - 20th level published Pathfinder AP. Plus the all the Faces of the Tarnished Souk, consist of exotic multi-class NPCs up to 20th level as support products for Coliseum Morpheuon might help...?

 

[Jester David]

At level 20, expect everyone in a party to be able to fly and have some resistance to energy. Magic items and spells mean it's hard to predict or anticipate the party's skills, since they're so wildly different. Given enough time, a party can easily be invisible, flying, stoneskinned, hasted, and more.

Low hitpoints can make a big difference if the party is able to unleash a full attack. Especially archers.
For spellcasters, avoiding a save or suck spell can make a world of difference.

For a final boss, just make sure they're over CR 20, and not only have healing, but a bodyguard that can take a hit or at least block line of sight for a round. Making them mythic to get an extra attack or action might also be good.
Giving the monster PC level gear and tricks of their own can also help. Or give them some extra ability score bumps for "reasons".

 

[Jeff Lee]

The monster creation rules are pretty much spot on, for monsters. They don't really mesh with class levels. You can have a monster with stats above or below the guidelines for its CR, but you don't want to venture too far away or it will be under/overpowered for its CR.

Sounds like you've got the making of a good fight, since you have minor baddies to provide support and distractions. Don't forget to use the environment to the enemy's advantage. They know the terrain; the PCs likely won't. The lair might have traps, cover, or other things that can provide enemies with an advantage, at least temporarily.