Rat Colony

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

Skyshaper

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

Nihil Spellbomb

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

Divest

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

Duress

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

Swamp

Geth's Verdict

Target player sacrifices a creature and loses 1 life.

Echoing Return

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

Echoing Decay

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

Suffocating Fumes

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

Typhoid Rats

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