It looks like Shvar Choryati (SC) has certain vulnerabilities:
- Evil undead. Not affected by blasphemy or life-drain.
- Golems. Not subject to spell-like effects, so immune to blasphemy. Non-living, so not affected by life-drain.
- Epic pseudonatural creatures with 21+ HD. They'll have a SR of 105, so SC's spell-like abilities won't affect them.
- Epic spells tailored to dismissing chthonic entities. Which I believe Mostin's cabal has available. SC might be too big for them to handle, though.
Creatures that are immune to SC's abilities might be able to hold it back. Regenerating creatures would be best- a mess of
dominated vampires, say. Although I doubt the bad guys would just sit around.
Also, I don't know how many necromancers are on the side of the good guys, so I don't know if the first is really an option. Nor do I recall reading about golems being used in combat, so the second is probably out, too. But it wouldn't surprise me if Mostin had a spell for calling an epic pseudonatural zombie hill giant or something; the third might provide something to hold SC back. But I think it the fourth is the most realistic possiblity. The spell devised for clearing out Azzagrat's chthonic entities might be powerful enough to deal with SC.
I guess we'll see.
