Dar'Thul, Vylnex's Necromancer

Hexproof from White
When Dar'Thul, Vylnex's Necromancer enters
the battlefield, return X creatures from all
graveyards to the battlefield where X is the
number black permanents you control.
At the beginning of your end step, you
may reveal the top card of your library.
If you do, each opponent loses life equal
to that card's converted mana cost.