First thing I did was use a summon demon spell and summoned my creature. Then I used the three potions from Barbatos that he makes for free from the book you get him in one of his quests. As soon as the chit chat ended, I immediately jumped backwards behind my summoned demon and creature. Then I just kept shooting level 5 explosive arrows and level 5 fireballs at everyone which I believe are the best because of the splash damage on all creatures within an area. My creature has a dragon elf head, so he was hurling level 7 fireballs as well. Anyone that approached me was smashed by my Barnabus' Mace with Life and Mana Leech and death sword dual wield combination.
Anytime I got low on health, I used a Greater Health Potion. Sure enough he was toast and ran to the teleport within a minute.
