Mestil's Acid Sheath
I found that the Demon Mephistopheles being highly resistant to most magic... is susceptible to acid! Acid bombs work wonders, especially if you haste your character and run around the cloud keeping him within its area of effect. Melfs acid arrow deals a bit, but by far the best technique when being a spell caster was Mestil's Acid Sheath, which did tremendous amounts of damage when he struck my character. However one must have a load of hitpoints, and some healing potions at his disposal.

Submitted By: Grahame