Covenant of Blood

{w} mana may be paid as though it were {p/w},
{u} mana may be paid as though it were {p/u},
{b} mana may be paid as though it were {p/b},
{r} mana may be paid as though it were {p/r},
{g} mana may be paid as though it were {p/g}.
Whenever an opponent pays life, you gain half
that much life, rounded down.
This card's color identity is Black.