Slya, Lady of the Damned

You can play Slya, Lady of the Damned from your graveyard.
{1}{w}{b}: You gain X life, which X is the number of Undead creatures in your graveyard.
{2}{b}{b}: Return a creature to the battlefield from your graveyard, if it is a Undead subtype, add a +1/+1 counter.
{3}{b}{r}: Add X +1/+0 counters to your creatures, which X is the number of Undead creatures in your graveyard.