Protection from acid, prot from fear, haste, chant. Strength potions if you have them. You actually should have at least a few. The game is very generous with these potions. Have two melee characters engage him. Look at which melee toon he is fighting. You want the melee character who is being targeted by Draconis to run around and stay out of reach. Eventually he will give up on that character and try to fight the next one. Do the same for this character. Have your casters use breach, pierce magic, and or other spells that remove magic protections. Do not use dispel magic, you will dispel your own buffs. After that, cast lower resist x3. Now keep hitting him with magic missile. Use your strongest healing potions when your characters are at least half health. Use the 6th level priest heal spell when needed.