Buried Citadel

This land enters the battlefield tapped unless you control a swamp or forest.
{t}: Add {b} or {g}
Whenever a permanent you control enters the graveyard, you gain life equal to its
converted mana cost.
Pay X Life: Return target permanent with
converted mana cost X or less to the battlefield,
but they are a zombie in addition to other types.
While the cities above flourish, the citadel zombies
feast on its remains.