[Dradeel]

If this is kurosian-the acid kensai, i remember UU's anwser on a post that asked a similar question and later i've also read it in his guide. He said that you should buy the crossbow firesth. I'm not good with names. The one you can buy on the roof of watchers keep and equip it with plain regular bolts. Than improve haste and kurosian should go down in a few rounds. I of course never tryed this but it seems plausible for his protections. It has something to do with fire damage from the crossbow getting trough his stoneskin and plain bolts i presume to get trough prot. from magic.