Umbra, Final Day's Twilight

Umbra, Final Day's Twilight costs {x} less to cast, where X is the amount of creatures you sacrifice while casting this spell.

When Umbra enters the battlefield, exile all other permanents.

When Umbra deals combat damage to a player, they take damage equal to the combined converted mana cost of all permanents exiled with Umbra, Final Day's Twilight.