evilin spell help

[Majere3]

I got this spell Evilin. I heard that this is undead rezz spell but I can't seem to get this work. I cast it on the corpse of my dead vamp. The spell didn't turn my vamp back.

I cast it on enemy corpse. It become a cloud of evilin. Then some enemy dragonfly flew into it. It kill some but there are no undead coming back.

Do I need to have full undead army for this spell to work? My army consists of vamp, archmage, inquistors, royal griffion, royal thorn.