Stormonu
Legend
Phantasmal killer and its big brother weird are both 3E illusions that kill people and aren't [shadow] spells (and thus not real at all). If I played 4e, I would assume any illusion spells that killed a target worked the same way -- scared 'em to death, essentially.
That, or go for "extreme psychosomatic reactions to illusionary/hallucinatory damage". Which is probably just a more technobabbly way of saying "scared 'em to death".
Somebody beat me with the Phantasmal Killer reference.
I guess it's like death in the Matrix. Your mind makes it real...