Rat Colony

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

Geth's Verdict

Target player sacrifices a creature of their choice and loses 1 life.

Defile

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

Echoing Decay

Target creature and all other creatures with the same name as that creature get -2/-2 until end of turn.

Skyshaper

Sacrifice this artifact: Creatures you control gain flying until end of turn.

Duress

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

Typhoid Rats

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

Divest

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

Swamp

Echoing Return

Return target creature card and all other cards with the same name as that card from your graveyard to your hand.

Nihil Spellbomb

{T}, Sacrifice this artifact: Exile target player's graveyard.
When this artifact is put into a graveyard from the battlefield, you may pay {B}. If you do, draw a card.

Suffocating Fumes

Creatures your opponents control get -1/-1 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)