Raldo:
Good! I must examine the other magic fields, meanwhile you should to the Dwarven Village. That is where the two devils most likely have gone.
Ask Filaur of the Gray Pillar of the Dwarven Village for the location of the magic field. They have probably sent a flock of succubus to drain it. Guard the field and when the evil creatures show up, kill them all! This is probably the last chance! If the magic field is destroyed 'the thing' will revive!