Help me create an encounter

[Weirdbob95]

Hello!

First of all, if you're in the Expeditions to the Ruins of Greyhawk campaign, stop reading now because of possible spoilers.

So, my party is going to meet Iuz (the Greyhawk demigod) soon, and, knowing them, will probably decide to fight him. He'll be in a weakened state due to plot events so he won't utterly destroy them. The encounter will be underground in a large room, a few rounds after another encounter with Iuz's general (a wizard). Although I've been mostly following the book, it recommends to have Iuz be impossible to fight, which I don't want to do.

The party, ECL 11 (maybe 12 by the time they get there):
Artificer/Warblade, crafted himself items to break WBL and has a ton of tricks up his sleeve
Psionic Warrior, uses Vigor+Share Pain and other buffs to tank hundreds of damage
Paladin of Freedom, can do a lot of damage on a charge with his new lance
Druid, likes to summon and buff grappling animals, other utility spells
Sorceror, focuses on blasting fire spells with some utility

They're all decently optimized and can kill enemies of higher CR than them.
For the actual encounter, I'm thinking Iuz would be a Horned Devil, without Regeneration or Summon Devil abilities, without the fly speed, but with a Divine Rank of 0 and no Divine Rank.

My questions:
How hard would the fight be?
Should I reduce the Horned Devil's defenses? AC 35 and SR 28 is hard for an ECL 11 party.
What would be the modified Horned Devil's CR?
Is there another demonic outsider that would be a better encounter?

[Wacky89]

so you want to make it weaker? Why are you making it immortal then, there is no point in them fighting the devil then.
You cannot kill something with a divine rank if you dont have one yourself

[Weirdbob95]

Good point. I originally gave it a Divine Rank to make it seem more god-like, but re-reading the divine rank rules, it doesn't help the flavor much but makes it much harder to defeat. Most of the interesting abilities require at least Divine Rank 1, but Divine Rank 0 creatures just get good defenses. They aren't invulnerable, however, as it says they can still be killed in combat.

[ace rooster]

The difficulty of that encounter changes radically with tactics. One of the heavily under-rated abilities is the devils 'see in darkness'. The best I can get do a vision range of 1200ft in darkness without it (and even that is directional, and grants concealment beyond 600ft. That +60 to hide gets annoying), and a devil can sit outside that range and wait for an opportunity. At will persistent image (range 1000ft) as a SLA gets funny if enemies burn resources every time they pretend to teleport into the middle of the group (remember true seeing lasts only a min per level). Observing standard tactics that the party will use is invaluable. Only having to hit once with an infernal wound to burn a few cures (with items not working due to caster level being too low) after they have left makes hit and run hugely effective.

On the other hand a creature with a speed of 20ft that takes full damage from electricity and has limited ranged ability could easily be taken on by a party lower than 11th level, if it doesn't use it's abilities well. A dimensional anchor can seriously cramp it's style, and then kiteing it with alchemical electrical damage is game over.

hope this helps.