Re: Q. about Firestorm
 

Undead Ermor has the easiest time using it, but C'tis, Utgård Jotunheim, Machaka, Carrion Woods, and Black Forest Vampire Counts (at least) can cast it. It does just brutal damage, and it is a great way to start a battle.

Re: Q. about Firestorm
 

yes, and i would just like to point out a little castle defence script of mine (very basic):
either raise skeles/hold , shadow blast and then either shadow again if you had an obscene amount of gems equip although i never do) or just repeat the first of raise skeles. the idea is that the enemy reaches the gate just in time to be nice and bunched up for a shadow blast from a bunch of mages