Aedin said:
My thinking is -1 LD from a vamp blood ability and -3 LD from Doom and darkness makes the banshee scream just as powerful as a Terrorghiests and your not going to stop his army from getting into close combat so you need some staying power.
Well, that assumes that
a) You can get the Vampire into a position where the daemon is in range of his aura.
b) You can get the banshees into position. Unlike terrorghiests, they can't fly (meaning they have much shorter movement, and can't hop over units). Also, they're far more vulnerable outside a unit, so will likely have to pick one unit to be in for protection.
c) You can get Doom and Darkness off. Well, you have to actually roll the spell (or spend quite a bit on magic, to make sure you get it). Since the DP is unbreakable, there's no reason to cast it on him, other than wanting to scream him to death. So, it seems very likely that your opponent will try to dispel such an obvious and dangerous threat.
Aedin said:
So 2 mortis engine scream and 3 more from banshees in a 2500pt list
Why the Mortis Engines? Are they key to the above plan in some way?