Dreadnought of Athreos

At the beginning of your upkeep, create three
Masks.
At the beginning of your end step, each creature
an opponent controls deals X damage to its
controller, where X is the number of Masks on
that creature.
Athreos is viewed as a merciful god by most of the
undead. Turns out, "most" of the undead haven't met
his dreadnoughts.