Well, I just got pretty far with a ratling Chaos Knight. The most interesting thing about the class, I think, is that it forces you to find non-standard solutions to many problems in the game.
I began with the mana battery corruption, which was a pain--your earliest corruptions are nearly impossible to get rid of. I was wondering if I would ever be able to complete the chaos trinity quests with that one, for example by dipping a wand in booze then giving it to the crone. But it became a moot point when dwarftown went hostile after I confused Thrundarr and scared Waldenbrook; the dwarves killed the mutated ratling.
Getting past the Eternal Guardian was very difficult. I didn't have a penetrating weapon throughout the game, so the only thing that helped me there was the acid blood mutation, which would occasionally blind one of the guardians and cause them to stagger around. With 7LB, I could sometimes get to move onto the staircase before another EG appeared. But by the time I died, there were 8 EGs on the level. :-( One of them finally killed me because I got the poison hands corruption during a fight and didn't switch gloved before drinking my potion of extra healing. Dumb! Even dumber, maybe, was returning to the surface so that I had to cross the EG a second time, which is what caused that fight in the first place. Wands of teleportation? Mana battery, remember?
Biggest challenges were getting Str and App exchanged by an unIDed potion, and going through most of the game without literacy. (Got it L19 at library--fortunately, you don't need to have the skill already to get it from the ghost librarian!)
Best weapon found was an eternium scimitar of devastation.
Thanks, Thomas!