I'm not sure if he really has that confusing attack. I think that the message "your surroundings suddenly look different" is not due to him confusing you, but instead it is displayed when the map of the chaos plane changes, which happens quite often. My two latest characters (who managed to get there that is) killed him in ranged combat and he hever confused them once.
While he definitely does have the ability to summon monsters, he would generally prefer spamming damaging spells at you.
I've also heard that throwing a blessed PoCC at him helps, but idk what the effects are. It says "andy looks weakened" and "andy seems burned by the liquid"