The King

All creatures you control gain the text:
"sacrifice this creature: add {b}
to your mana pool."'
All other zombies gain +2/+2
The King's power cannot be higher than 0.
{b}: Place a -1/-1 counter on target creature.
{x}{t}: Search your graveyard for a creature
with the zombie subtype with a
converted mana cost of X or lower.
Put it onto the battlefield.