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.)

Sol Ring

Swamp

Swarm of Rats

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

Drainpipe Vermin

When this creature dies, you may pay {B}. If you do, target player discards a card.

Voracious Vermin

When this creature enters, create a 1/1 black Rat creature token with "This token can't block."
Whenever another creature you control dies, put a +1/+1 counter on this creature.

Aspect of Gorgon

Enchant creature
Enchanted creature gets +1/+3 and has deathtouch. (Any amount of damage it deals to a creature is enough to destroy it.)

Skullsnatcher

Ninjutsu {B} ({B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever this creature deals combat damage to a player, exile up to two target cards from that player's graveyard.

Thornplate Intimidator

When this creature enters, target opponent loses 3 life unless they sacrifice a nonland permanent or discard a card.
(This token's mana cost is {3}{B}.)

Typhoid Rats

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

Aspect of Lamprey

Enchant creature you control
When this Aura enters, target opponent discards two cards.
Enchanted creature has lifelink.

Offspring {3} (You may pay an additional {3} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature enters, target opponent loses 3 life unless they sacrifice a nonland permanent of their choice or discard a card.

Afflict

Target creature gets -1/-1 until end of turn.
Draw a card.

Ruin Rat

Deathtouch
When this creature dies, exile target card from an opponent's graveyard.

Sinuous Vermin

{3}{B}{B}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has menace. (It can't be blocked except by two or more creatures.)

Aspect of Manticore

Flash
Enchant creature
When this Aura enters, enchanted creature gains first strike until end of turn.
Enchanted creature gets +2/+0.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Gnat Miser

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

Burglar Rat

When this creature enters, each opponent discards a card.

Graf Rats

At the beginning of combat on your turn, if you both own and control this creature and a creature named Midnight Scavengers, exile them, then meld them into Chittering Host.

Razortooth Rats

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

Bake into a Pie

Destroy target creature. Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Nezumi Linkbreaker

When this creature dies, create a 1/1 red Mercenary creature token with "{T}: Target creature you control gets +1/+0 until end of turn. Activate only as a sorcery."

Midnight Scavengers

When this creature enters, you may return target creature card with mana value 3 or less from your graveyard to your hand.
(Melds with Graf Rats.)

Arcane Signet

Ravenous Rats

When this creature enters, target opponent discards a card.

Arc Lightning

Arc Lightning deals 3 damage divided as you choose among one, two, or three targets.

Agonizing Demise

Kicker {1}{R} (You may pay an additional {1}{R} as you cast this spell.)
Destroy target nonblack creature. It can't be regenerated. If this spell was kicked, Agonizing Demise deals damage equal to that creature's power to the creature's controller.

Aphetto Dredging

Return up to three target creature cards of the creature type of your choice from your graveyard to your hand.

Crypt Rats

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

Totentanz, Swarm Piper

Whenever Totentanz or another nontoken creature you control dies, create a 1/1 black Rat creature token with "This token can't block."
{1}{B}: Target attacking Rat you control gains deathtouch until end of turn.

Mukotai Ambusher

Ninjutsu {1}{B} ({1}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Lifelink

Daggerfang Duo

Deathtouch
When this creature enters, you may mill two cards. (You may put the top two cards of your library into your graveyard.)

Mountain

Barbed Batterfist

For Mirrodin! (When this Equipment enters, create a 2/2 red Rebel creature token, then attach this to it.)
Equipped creature gets +1/-1.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Chittering Host

Haste
Menace (This creature can't be blocked except by two or more creatures.)
When this creature enters, other creatures you control get +1/+0 and gain menace until end of turn.

Annihilating Fire

Annihilating Fire deals 3 damage to any target. If a creature dealt damage this way would die this turn, exile it instead.

Muck Rats

Pestilence Rats

Pestilence Rats's power is equal to the number of other Rats on the battlefield. (For example, as long as there are two other Rats on the battlefield, Pestilence Rats's power and toughness are 2/3.)

Nezumi Informant

Nezumi Cutthroat

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

Ossuary Rats

When this creature enters, it deals X damage to target creature or planeswalker an opponent controls, where X is the number of creature cards in your graveyard.

Chittering Rats

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

Ardent Elementalist

When this creature enters, return target instant or sorcery card from your graveyard to your hand.

Relentless Rats

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

Disease Carriers

When this creature dies, target creature gets -2/-2 until end of turn.

Auger Spree

Target creature gets +4/-4 until end of turn.

Refurbished Familiar

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Flying
When this creature enters, each opponent discards a card. For each opponent who can't, you draw a card.

Rat Colony

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

Okiba-Gang Shinobi

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 this creature deals combat damage to a player, that player discards two cards.

Gutter Skulk

Gobhobbler Rats

Hellbent — As long as you have no cards in hand, this creature gets +1/+0 and has "{B}: Regenerate this creature." (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)