Swamp

Crypt Rats

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

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

Target player sacrifices a creature of their choice.

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

When Ravenous Rats enters, target opponent discards a card.

When this creature enters, each opponent discards a card.

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

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

Target player reveals their hand. You choose a nonland card from it. That player discards that card.

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.