Eviln is a Chaos spell that summons a dark cloud from a corpse that either kills living creatures or recovers a % of fallen under units that walks on it (both yours and enemy's).
Since it recovers a %, this means the more Black Knights you have, the bigger the number of recovered units.
Here's another power combo for you. Play Mana/Intelligence-based Paladin, use black knights, use 3 spells: Stone Skin, Eviln and Armageddon. Use the pet dragon to transform rage to mana (so that you can cast consecutive armageddons - mind you, they are astral damage, so dragons are not a good idea) and rule any arena
EDIT: Here's a link to a clip I made based on the last strategy I explained:
http://forum.1cpublishing.eu/showthr...nt+day+paladin