Hmm.. here are most of the creatures I found most vulnerable to death spell:
*Goblin
*Duergar
*Umberhulks
*Yuan-ti
*Peasants (well they are vulnerable to death spell
)
*Wyverns
*Orcs
*Ogres (Ogre mage, Ogre ETC....)
*Hostile animals (Tiger, Rabbit, Mountain Lion ETC....)
*Elementals (Well some of them are vulnerable to death spell, but not all of them)
*Knolls
*Trolls (sometimes they just get knocked down by the spell, use fire or acid to kill it)
Well that's all I can think of (for now atleast [img]smile.gif[/img] )Other creatures are Vulnerable to death spell. But I guess its up to you now to discover them.