Eresh, Dominion of Fools

(Eresh, Dominion of Fools is all colors.)
Eminience — While Eresh, Dominion of Fools is on the battlefield or in the command zone, whenever a source you control would add mana, exile the top card of your library instead. Additionally, when you pay the cost of a spell or ability, each card exiled by this effect that you return to the bottom of your library reduces that cost by {1} or one mana of tha