Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

Whenever you tap a Swamp for mana, add an additional {B}.

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

{B}, Discard a card: Regenerate Dirty Wererat.

Threshold -- As long as seven or more cards are in your graveyard, Dirty Wererat gets +2/+2 and can't block.

When Gray Merchant of Asphodel enters the battlefield, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

{2}{B}: Infected Vermin deals 1 damage to each creature and each player.

Threshold -- {3}{B}: Infected Vermin deals 3 damage to each creature and each player. Activate only if seven or more cards are in your graveyard.

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)

Other Rats you control have toxic 1.

When Karumonix enters the battlefield, look at the top five cards of your library. You may reveal any number of Rat cards from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in a random order.

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

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.

{B}, Sacrifice a creature: Target player discards a card. Activate only as a sorcery.

Whenever another nontoken creature dies, you may create a 1/1 black Rat creature token.

Rats you control have deathtouch.

Ninjutsu {3}{B} ({3}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)

Whenever Okiba-Gang Shinobi deals combat damage to a player, that player discards two cards.

Rats you control have menace.

{1}{B}, {T}: Create a 1/1 black Rat creature token.

{2}{B}{B}, {T}, Sacrifice three Rats: Gain control of target creature.

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)

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.

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.

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.

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.

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.

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.

Shadow (This creature can block or be blocked by only creatures with shadow.)

Whenever Stronghold Rats deals combat damage to a player, each player discards a card.

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