Malagog, Nefaria’s End

Flying, lifelink, shroud
When Malagog, Nefaria's End enters the battlefield, each opponent loses X life, where X is
your devotion to black. You gain life equal to the
life lost this way. (Each {b} in the mana costs of permanents you control counts toward your devotion to
black.)
Whenever you gain life, target opponent loses
that much life.