mono black board control

Each land is a Swamp in addition to its other land types.

At the beginning of each player's upkeep, that player sacrifices a non-Zombie creature of their choice. At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.

All Swamps are 1/1 black creatures that are still lands.

Destroy all creatures you don't control. They can't be regenerated.