Dargoth, Disciple of Bolas

Eminence — At the beginning of your upkeep, if Dargoth is in the command zone or on the battlefield, exile the top card of target player's
library. You may cast that card for as long as it
remains exiled, and you may spend mana as
though it were mana of any type to cast that spell.
Whenever you cast a spell you don't own, create a
3/2 black Zombie Horror creature token with
haste.