Help I am trapped in a book, in a temple, with a devil that doesn't seem to get hurt.

I read a book in the great library and found myself in it. Talked to a young man and should have tried to cure his blindness, but went in to the temple. Scouted in inviso to see what I was up against. Attacked with fireball, ran, attacked again when they wern't looking, then pounded the unholy crusaders and the matron mother until I was victorious. All of this in another room from big red and grusome. Then I went for him only to find nothing hurts him. I reloaded (its obvious I got butt kicked) and tried inviso to get arounf him and pick up the items behind him. Well that gave me some items including armor which I think a particular medusa won't like. but nothing I can use against him. Also no key to get into the locked room.

Now I find I can't back out of the temple. Its a readers nightmare. Any ideas on how to deal with the red devil.

I am a sorcerer with the half-orc. The best we have are +1 weapons.

A critical hit or two should do the trick. He has something like 25/+2 or 25/+3 damage resistance, so if Xanos has an axe of any kind, a single critical hit should severely damage him.

Actually walked around the creep using Invisibility. Met a dead wizard and his friend, got some information, and then went out and completed the other winds before coming back. Now I can't seeme to get this guy and am wondering if its because I didn't nail the devil. Should I get a +2 weapon for Xanos and try and slug it out with him. or should I go back and try a different tactic.