So we finished our Rise of the Runelords campaign yesterday. We started in September of 2014 and it has been almost 60 sessions. We've all had a blast. Big thanks to Paizo for making such a fun adventure, and another thanks to all forum posters here for helping in scorching-raying away the AP's warts.
Here's how the end battle against Karzoug went down (as I can recall it, it went late and there was some beer involved), hope it can be of use to other GMs.
Preamble:
We're a gang of old timers who've returned to this hobby after many years. I have four PCs in the group, all level 16. A cleric of Desna, a ranged ranger, an evoker wizard and a two-handed fighter. I let the players roll in a very generous fashion which gave them have silly high stats (something I regretted after we all had picked up speed again), and also Hero Points. They had quite well built characters, with loads of HP and crazy saves, and were really well decked out due to crafting feats and smart acquisitions. They all had runeforged weapons. Karzoug's tactics and spells, and some of his equipment, were adjusted by me as a consequence.
I revised Karzoug's spell list. He used most of his transmutation slots for buffs instead of attack spells, since he knew the PCs had Dominant weapons. I gave him metamagic gemstones, 3 of each kind, so he could cast more quickened spells (and silent ones as well) than his rod allowed. Also I added a bunch of scrolls and some other bits and pieces. I replaced his Arcane Strike and Combat Expertise with Spell Penetration and Improved Initiative. He also had Boots of Speed. I had pre-rolled the rounds for his two time stops, and made a spreadsheet for him and his minions' actions for the fight. I also allowed Karzoug the see the whereabouts of the PCs - they all wore Rings of Xin-Shalast, so he would pre-buff before they entered the Anima Focus. I had given all Karzougs minions the advanced template to make them last more than one round.
The Eye:
The PCs buffed themselves to the teeth, and then some more (they'd spent plenty on scrolls, both self-crafted and bought ones) and readied themselves. Then they jumped in. Big K had prepped with an widened (from gemstone) Dimensional Lock at the arrival platform, to prevent them from just hopping up to him. He had placed two symbols, (pain and weakness) on the stairs up (which his guards were attuned to). He'd placed a Wall of Suppression across the chamber, but with a gap at the top so he could fly over it. He had a permanent Prismatic Sphere 20 ft. above his throne. He himself was hovering above the sphere, invisible from a UMD:d wand. He had his Glaive project an major image of him sitting on the throne as a decoy, hoping the PC's would attack it (and so I could show my players the awesome cover of Gamemastery Guide). He hoped they would notice they couldn't Dimension Door/Hop up, so they would run or fly up to him at the throne, through the Wall and over one of the symbols. Unfortunately for old Karzy, that's not how it went down though.
Karzoug's buffs at the start of the fight:
Fiery Body (from scroll - he's the Runelord of greed, he's got some bling)
Mind Blank
Spell Turning
Stone skin
Haste (from boots)
Protection against Fire
Protection against Electricity
Protection against Cold
Fire resistance (he knew the wizard liked his fire spells)
Electricity resistance
Cold resistance
Invisibility
Protection from good
False Life
The PC's buffs - too many to list, but some will be mentioned in the round-by-round description. Mainly, they all had loads of elemental resistance/protection, death ward, true seeing, displacement, protection from spells (+8 res bonus!), stoneskin and other goodies. They had to save some round-only buffs to the fight (haste, mirror image, holy aura). They suspected (rightly) that he would go for necromancy and evocation in his attacks, since they thought that he knew that they had Dominant weapons...
The fight:
Round 1
All pc's easily make their saves from the stun from being transported by the Anima Focus (I add +2 to +5 to all DC's to try to somewhat counter the incredible saves my pc's have). They quickly take in their surroundings. The ranger rolls a perception check, rolls crazy high, and sees both the Wall of Suppression (which wasn't hard) and the two symbols (which was harder). He tells the other's through their permanent telepathic bond. They thought that the Wall was a Wall of Force, and took note to stay away from the symbols (although I forgot about them at the end of the fight). They all see that the Karzoug on the throne is an illusion (all have true seeing) and the the real Karzoug is flying, body immolated, above the primatic sphere atop the throne.
Karzoug wins initiative (I rolled a 20). Meteor Swarm (was thinking to change this rather weak tactic, but thought it would be a nice opener nevertheless) on the cleric, who takes a little damage, and a little fire damage that is absorbed by the party's protection from fires. Then time stop, four rounds.
Karzoug casts globe of invulnerability on himself, flies down to the PC's. We use the action economy from Pathfinder Unchained. So next round, he positions himself next to the wizard, casts a Prismatic Sphere around the both of them, steps out, flies back (over his Wall), casts a Delayed Fireball at the pc's and goes into his permanent prismatic sphere at the throne.
The time stop ends, the delayed fireball explodes and shaves off some more resistance and damages them (except the wizard, who is safe in his new cozy home).
The dragons flies down, through the wall (no buffs) which the PCs though was a weird Wall of Force. He breathes lightning in a flyby attack, by the PCs continue in making their reflex saves so just a little damage. The PCs attack the giants, the wizard tries to dimension door out, and understanding he can't, curses himself for using their mage's disjunction scroll on the door in to the anima focus before.
The runegiant Hutta gets hit with loads of damage from the ranger, misses a wisdom check and discards her orders to get the PC's to come up through the traps. She will show her lord how worthy she is of being his bodyguard by defeating these pesky humans herself! She moves down the platform, passes through the Wall, casts True Seeing on herself to see through the displacement all the PC's have. The fighter airwalks up to one storm giant and engages him, and he strikes back. The other storm giant uses his Chain lightning which shaves off some HP here and there. The cleric who's gotten the brunt of it all the first round casts a Heal on himself. You know it's gonna be a great fight when Heal comes out the first round. People that say in-combat healing is a waste obviously don't play at this level... ;-)
Round 2
Karzoug comes out of his Sphere, casts a quickened Horrid Wilting, damages the PC's some, and flies back in again. The wizard tells the cleric to dispel the dimensional anchor so he can come out, and readies a dimension door for the cleric's cue. The cleric casts a dispel on the anchor, and uses a Hero Point (the first of many to be spent in this fight, they saved the day). With the Hero Point, the player rolls 32 (needed a 31 to dispel it). Meanwhile the ranger hurts the runegiant, but is getting trashed by a crit from the runegiant's retaliation and arrows from a storm giant. With the damage from here and there and the Horrid Wilting, he's just got a few hit points left. If Karzoug hits him with spell at the start of round 3 he'll be gone. Karzoug, seeing it all from his safe little tree house, sharpens his finger of death for the next round. The fighter melees with the other stormgiant, and downs him.
Round 3
The ranger uses a Hero Point to change his initiative to first in the round, before Karzoug. He uses a teleporting arrow to get away up to the side, and drinks a CSW potion. Karzoug comes out and throws a Wail of the Banshee at the other pc's, he can't reach the ranger now on one round. The wizard recognizes the spell with a Spellcraft roll, and tells everyone to watch out. Everyone uses Hero Points for their saves, and all make it, with some close calls. Karzoug doesn't fly back though, but remains hovering above the party, full of arrogance and getting really annoyed. How could these worms still be alive? Preposterous! The fighter attacks the runegiant, who attacks him back. The cleric casts greater dispel at Karzoug and gets rid of his Fiery Body, Stoneskin and Globe of Invulnerability. They players really roll well the whole night. The wizard casts interposing hand to try to get away from the dragon, who's flown around to the back and is making short order of his mirror image, and a quickened scorching ray at the dragon.
Round 4
The ranger peppers Karzoug with all he's got, but luckily for the BBEG he doesn't score a crit on his now crit-vulnerable self. Karzoug casts his second timestop, and casts a quickened summon for an elder air elemental, which he orders to disarm the fighter. He also casts repulsion and ice body on himself to get crit immunity again, and gets ready to maze the fighter. The fighter fights the runegiant, blinds and staggers her with a crit and gets attacked by the newly arrived air elemental, who misses to disarm him. The ranger downs the runegiant. The wizard Banishes the air elemental, who hardly had time to say Hello. The cleric hits all PCs with a Mass Heal from a scroll.
Round 5
Karzoug mazes the fighter, who's player declines doing the real maze that I've printed out for him and instead rolls an Int check, using a Hero Point. He needs to roll above 11, and makes it. He's back next round. The dragon tears in on the cleric and the wizard, who fight back. The wizard shows that he also has big boy spells, and mazes the remaining storm giant, who's been peppering the pc's with arrows. The ranger attacks Karzoug. Karzoug releases his glaive who starts fireballing left and right, but due to low DC isn't doing much damage. The cleric casts Holy Aura, giving all Spell Resistance 25, which would prove really valuable later on.
Round 6
Karzoug smiles and Wishes him and all his bodyguards back to full life and health. The pc's squeal. Karzoug moves in for a Finger of Death on the cleric the next round, thinking that the fighter is gone for a while and with his allies back he's practically won. The fighter comes back, which makes Karzoug roar in anger. Enough! Die! The wizard and the dragon battle it out, the ranger lets his arrows fly.
Round 7
Karzoug tries to Finger of Death the cleric, but I roll a 2 on Karzoug's spell penetration (he needed a 3 or more to get over the Spell resistance of 25!). This becomes a turning point for old Karzy. The cleric summons an air elemental who engages the body guards, while the wizard greater dispels some of Karzoug's buffs. The ranger and fighter battles it out with the minions.
Round 8-9
Wild fighting, spells zapping back and forth between Karzoug and the wizard's spell turnings, the giants and dragon gets killed, Karzoug dimension doors back to heal himself in his permanent Prismatic Sphere, comes out and attacks the wizard with a polar ray which he survives. The fighter tries to close with Karzoug but can't pass his repulsion.
Round 10+
The wizard manages to dispel both Karzougs repulsion (they were great at dispelling) and wreath of blades. The cleric dimension hops up with the fighter close to Karzoug with a Silence on the fighter. Karzoug uses a silent gemstone to dispel the silence - he should have used it for a dimension door away instead. I was getting a bit tired here. Everyone attacked Karzoug who answered with Caustic Combustion and a second Wail. But he couldn't withstand the barrage, even if he was still immune to crits. So he went down, with a last cry of "Impossible! I'm a God! Why can't I live on?" (brownie points for anyone who knows where that is from...)
And that ended our campaign. The fight took almost four hours of straight gaming. The PC's fared really well, with their planning, buffing and dispelling really paying off (along with some luck and Hero Points to help tip the scales...) Now it's on to Hell's Rebels!