So seeing as how Svenn had generously popped Emperor Chottal, I decided to give him a whirl.
Round 1: Tried to gnomecheat through the door when the Blood of Chottal was up, got quadded a bunch of times for 160 each and capped.
Round 2: Pulled out the stupid blood and killed him (had to rune my pet twice). Sent in a skeletal guardian and got horrible charm breaks and pyrocuored and I forgot to empty my top slot, so I clicked off all my buffs, cancelled pyrocuor, and camped out. My pet actually died with 4 seconds left, but chottal couldn't summon me because he'd summoned my pet recently
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Round 3: Sent in the EB, it did OK but not really that well. After it died I stringsed a skeletal guard, but charm broke fast and I died. Had him down to 80% or so.
Round 4: After CR, killed two of his guards and the duke in an attempt to clean up the room a bit. My plan was to rapture chottal and have my pet beat his down quickly while I got some slow attempts. It turns out Chottal is immune to rapture. I just capped in disgust.
So, for those keeping score, Chottal is kind of a badass. I asked Ambrotos to check his mana, and he has 9000 or so in addition to the 18000 hp according to macroquest. Pretty crazy.
Also for aspiring enchanters, the solo god mode mobs known to be immune to rapture are the Sebilite Protector, Chottal, and Korocust, while Tolapumj and the Spore king are not. I think Neh might be immune as well, and I haven't tried Rak, Phinigel, the Fear golems, or the Protector of Sky.