Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Sewer Rats

{B}, Pay 1 life: Sewer Rats gets +1/+0 until end of turn. Activate no more than three times each turn.

Swamp

Ravenous Rats

When Ravenous Rats enters, target opponent discards a card.

Crypt Rats

{X}: Crypt Rats deals X damage to each creature and each player. Spend only black mana on X.

Divest

Target player reveals their hand. You choose an artifact or creature card from it. That player discards that card.

Chainer's Edict

Target player sacrifices a creature of their choice.
Flashback {5}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Rat Colony

Rat Colony gets +1/+0 for each other Rat you control.
A deck can have any number of cards named Rat Colony.

Burglar Rat

When this creature enters, each opponent discards a card.

Cast Down

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Plague Rats

Plague Rats's power and toughness are each equal to the number of creatures named Plague Rats on the battlefield.

Chittering Rats

When Chittering Rats enters, target opponent puts a card from their hand on top of their library.