NPC necromancers using non-classic DS
 

Couldn't find the date Shield of Torment (id 3609) was introduced, but it doesn't exist in Velious spdats so must be Luclin/PoP at the earliest.

Are you sure they aren't casting Banshee Aura?

How do you know the exact buff spell they are casting?

The necro NPC's I've seen say "X is surrounded by a shrieking aura.", which is the Banshee Aura message.

Yeah, I was wrong, it must be Banshee Aura after all.