I'd recommend attacking it.
But seriously, if it's giving you trouble, you're going to have to give us some details about what your party is like. How many characters do you have, and what classes are they? What spells are your mages using? Do you have a lot of potions, or healing spells, or use summons? Do you have the expansion Legends of Aranna? Answering these will let me give you a good strategy to take that guy down.
One more thing--in the future, if you have multiple questions, it may be a bit easier for people to reply if you post all your questions in a single thread. And, of course, welcome to the forum! We'll gladly field any more questions you might have.