Tomb of the Serpent Kings

Tomb of the Serpent Kings enters the battlefield tapped.
{t}: Add {u},{b} or {g}, pay 2 life.
{x}: Sacrifice Tomb of the Serpent Kings: Search
your graveyard for a creature card with converted
mana cost X or less and put it onto the battlefield.
It's a Zombie in addition to its other types. If it's
a Snake or Naga, it gains haste until end of turn.
At the beginning of the end step, exile every
creature put on the battlefield by this effect.