Pretty sure the sanctum East of udgaard, where mobs in part of the area are hyper vulnerable to a specific kind of attack from a wand or talisman.

Failing that, potentially a muter, as certain disrupt spells do huge damage once you have landed a couple of maladictions (soften and decalcify).

Also I seem to recall that sometimes works outside udgaard took unspeakable damage for no obvious reason, when they probably shouldn't have.

Finally there's the old underwater lighting spells.