Uhhh,
@BoneyM Is this thing cannon?
Banish Undead
Casting Number: 26
Casting Time: Full action
Ingredient: A vial of blessed water (+3)
Description: You create a magical vortex within 48 yards (24 squares)
that sucks energy from the Undead.
Use the large template.
Those Undead affected take a Damage 5 hit, unless they are
Skeletons or Zombies, which are instantly destroyed instead.
I think that casting number would put it squarely in the Fiendishly Complex rating. But. It's not battle magic. And it is a 100meter diameter vortex that instant kills skeletons and zombies. That said, it is a necromancy spell. I'm just not sure if it is cannon to the quest.
At a guess, comparing this to the Second Secret, using this makes you look more like a Necromancer (it is a Necromancy spell) but is less likely to leak the First Secret of Dhar.
A hundred meter diameter circle is probably more than enough to kill a couple of squads of undead chaff. Hell, it could evaporate part of an undead army. But this is real necromancy, so I'm not sure where to rank it compared to Second Secret usage, with everything we know about Dhar and the gear Mat has.
Second Secret is a "There is an Undead Apocalypse". Hopefully we just stopped that, so we won't need to use it if the Dead from the Sands don't march on Karag Eight Peaks. Or one of the other Karags, and Belegar sends us to help.
But this Banish Undead thing sounds like the kind of thing you might be able to study the theory of, and try and work out how an Amethyst (Shyish) mage might cast a variant of it. Or did someone already do that, and that's how Wind of Death was invented?
Huh. Now that I think about it, this sounds like it has stuff in common with Pit of Shades as well.
EDIT: That blessed water bit makes me thing maybe this thing is Necromancy in name only. Not likely, but hey, maybe it's less evil Necromancy? I kid, I kid.