Tourach's Canticle

Target opponent reveals their hand. You choose a card from it. That player discards that card, then discards a card at random.

Unearth

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Blood Beckoning

Kicker {3} (You may pay an additional {3} as you cast this spell.)
Return target creature card from your graveyard to your hand. If this spell was kicked, instead return two target creature cards from your graveyard to your hand.

Piper of the Swarm

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.

Death's Duet

Return two target creature cards from your graveyard to your hand.

Swarm of Rats

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

Assassinate

Swamp

Swarmyard

{T}: Add {C}.
{T}: Regenerate target Insect, Rat, Spider, or Squirrel. (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Doomfall

Choose one —
• Target opponent exiles a creature they control.
• Target opponent reveals their hand. You choose a nonland card from it. Exile that card.

Ogre Slumlord

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

Rat Colony

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

Mind Rot

Casting of Bones

Enchant creature
When enchanted creature dies, draw three cards, then discard one of them.

Unholy Indenture

Enchant creature
When enchanted creature dies, return that card to the battlefield under your control with a +1/+1 counter on it.

Heartless Act

Choose one —
• Destroy target creature with no counters on it.
• Remove up to three counters from target creature.

Drainpipe Vermin

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

Patron of the Nezumi

Rat offering (You may cast this spell any time you could cast an instant by sacrificing a Rat and paying the difference in mana costs between this and the sacrificed Rat. Mana cost includes color.)
Whenever a permanent is put into an opponent's graveyard, that player loses 1 life.

Omen of the Dead

Flash
When Omen of the Dead enters, return target creature card from your graveyard to your hand.
{2}{B}, Sacrifice Omen of the Dead: Scry 2.

Typhoid Rats

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

Pack Rat

Pack Rat's power and toughness are each equal to the number of Rats you control.
{2}{B}, Discard a card: Create a token that's a copy of Pack Rat.

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.)

Ratcatcher

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
At the beginning of your upkeep, you may search your library for a Rat card, reveal it, put it into your hand, then shuffle.

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.

Ravenous Rats

When Ravenous Rats enters, target opponent discards a card.

Crypt Incursion

Exile all creature cards from target player's graveyard. You gain 3 life for each card exiled this way.