Ravenous Rats

When Ravenous Rats enters, target opponent discards a card.

Ruin Rat

Deathtouch
When Ruin Rat dies, exile target card from an opponent's graveyard.

Swarm of Rats

Swarm of Rats's power is equal to the number of Rats you control.

Locust Miser

Each opponent's maximum hand size is reduced by two.

Marrow-Gnawer

All Rats have fear.
{T}, Sacrifice a Rat: Create X 1/1 black Rat creature tokens, where X is the number of Rats you control.

Rancid Rats

Skulk (This creature can't be blocked by creatures with greater power.)
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Typhoid Rats

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

Relentless Rats

Relentless Rats gets +1/+1 for each other creature on the battlefield named Relentless Rats.
A deck can have any number of cards named Relentless Rats.

Crypt Rats

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