Savage orc shaman Fireball spam.

[Astegard]

When savage orc shamans in the mongrelwoods orcs quest set their mind to it they spam fireballs endlessly.

This happened to my party at the end of the quest where I had to save against 9 fireballs of high caster level from one regular shaman.
Considering you are expected to fight the boss at the same time, this is near impssible without fire immunity.