Malior d'Phiarlan

Partycrashers
When you first enter the ballroom, you can find him near the big fountain, talking to a group of Phiarlan Retainers. He will say:
 * Malior d'Phiarlan: Hello there! How are you this fine day?

If you can see his true nature, you can talk to him about this:
 * Malior d'Phiarlan: Hello there! How are you this fine day?
 * You: (Bluff) I heard that the Phiarlan Captain of the Guard is recalling all of his troops to some kind of briefing in the Library.
 * Malior d'Phiarlan: (Failure) Really? I didn't know that House Phiarlan has a "Captain of the Guard"... that sounds more like House Deneith's style, don't you think?
 * Malior d'Phiarlan: (Success) ??????????????????
 * You: (Intimidate) I know who you are, and you can't hide in this Ballroom forever. Come with me and settle this now, or one day you'll end up face-down in a dark alley!
 * Malior d'Phiarlan: (Failure) ??????????????????
 * Malior d'Phiarlan: (Success) But... no... there's no need to be hasty!
 * Malior d'Phiarlan: I don't want any trouble. Just tell me where you want me to go.
 * You: To the Library. Now.
 * You: (True Seeing) You have these guards eating out of your hand, but they can't see what I see... you're a Tiefling!
 * Malior d'Phiarlan: Indeed? How observant of you!
 * Malior d'Phiarlan: Still, I fail to see what you can possibly do about it. If you attack me, my new guard friends shall undoubtably defend me.
 * Malior d'Phiarlan: Why, I imagine you would make an enemy of all House Phiarlan if you disrupted their little soiree.

If you can lure him to the library, you will have to fight him.