Lab Rats

Buyback {4} (You may pay an additional {4} as you cast this spell. If you do, put this card into your hand as it resolves.)
Create a 1/1 black Rat creature token.

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.

Blightbelly Rat

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Blightbelly Rat dies, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Necrotic Fumes

As an additional cost to cast this spell, exile a creature you control.
Exile target creature or planeswalker.

Ayara, First of Locthwain

Whenever Ayara, First of Locthwain or another black creature you control enters, each opponent loses 1 life and you gain 1 life.
{T}, Sacrifice another black creature: Draw a card.

Mage Hunters' Onslaught

Destroy target creature or planeswalker.
Whenever a creature blocks this turn, its controller loses 1 life.

Bladebrand

Target creature gains deathtouch until end of turn.
Draw a card.

Phyrexian Atlas

{T}: Add one mana of any color.
Corrupted — Whenever Phyrexian Atlas becomes tapped, each opponent who has three or more poison counters loses 1 life.

Make Obsolete

Creatures your opponents control get -1/-1 until end of turn.

Opal Palace

{T}: Add {C}.
{1}, {T}: Add one mana of any color in your commander's color identity. If you spend this mana to cast your commander, it enters with a number of additional +1/+1 counters on it equal to the number of times it's been cast from the command zone this game.

Crypt Rats

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

Obelisk of Urd

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
As Obelisk of Urd enters, choose a creature type.
Creatures you control of the chosen type get +2/+2.

Unlikely Aid

Target creature gets +2/+0 and gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Rat Colony

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

Sorin's Thirst

Sorin's Thirst deals 2 damage to target creature and you gain 2 life.

Rabid Rats

{T}: Target blocking creature gets -1/-1 until end of turn.

Corrupt

Corrupt deals damage to any target equal to the number of Swamps you control. You gain life equal to the damage dealt this way.

Nezumi Informant

When Nezumi Informant enters, each opponent discards a card.

Dead Revels

Spectacle {1}{B} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Return up to two target creature cards from your graveyard to your hand.

Ghoulcaller's Chant

Choose one —
• Return target creature card from your graveyard to your hand.
• Return two target Zombie cards from your graveyard to your hand.

Gravepurge

Put any number of target creature cards from your graveyard on top of your library.
Draw a card.

Scrib Nibblers

{T}: Exile the top card of target player's library. If it's a land card, you gain 1 life.
Landfall — Whenever a land you control enters, you may untap Scrib Nibblers.

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.

Tanglebloom

Septic Rats

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Whenever Septic Rats attacks, if defending player is poisoned, it gets +1/+1 until end of turn.

Scourge of Nel Toth

Flying
You may cast Scourge of Nel Toth from your graveyard by paying {B}{B} and sacrificing two creatures rather than paying its mana cost.

Drag to the Bottom

Domain — Each creature gets -X/-X until end of turn, where X is 1 plus the number of basic land types among lands you control.

Gnawing Vermin

When Gnawing Vermin enters, target player mills two cards.
When Gnawing Vermin dies, target creature you don't control gets -1/-1 until end of turn.

Leaden Myr

Vat Emergence

Put target creature card from a graveyard onto the battlefield under your control. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cradle to Grave

Destroy target nonblack creature that entered this turn.

Mortuary Mire

Mortuary Mire enters tapped.
When Mortuary Mire enters, you may put target creature card from your graveyard on top of your library.
{T}: Add {B}.

Ichor Shade

At the beginning of your end step, if an artifact or creature was put into a graveyard from the battlefield this turn, put a +1/+1 counter on Ichor Shade.

Cryptic Caves

{T}: Add {C}.
{1}, {T}, Sacrifice this land: Draw a card. Activate only if you control five or more lands.

Ogre Slumlord

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

Elspeth's Nightmare

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Destroy target creature an opponent controls with power 2 or less.
II — Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.
III — Exile target opponent's graveyard.

Wail of the Nim

Choose one —
• Regenerate each creature you control.
• Wail of the Nim deals 1 damage to each creature and each player.
Entwine {B} (Choose both if you pay the entwine cost.)

Cultist of the Absolute

Commander creatures you own get +3/+3 and have flying, deathtouch, "Ward—Pay 3 life," and "At the beginning of your upkeep, sacrifice a creature."

Parasitic Grasp

Cleave {1}{B}{B} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Parasitic Grasp deals 3 damage to target [Human] creature. You gain 3 life.

Oversold Cemetery

At the beginning of your upkeep, if you have four or more creature cards in your graveyard, you may return target creature card from your graveyard to your hand.

Chittering Skitterling

Corrupted — Sacrifice an artifact or creature: Draw a card. Activate only if an opponent has three or more poison counters and only once each turn.

Ravenous Rats

When Ravenous Rats enters, target opponent discards a card.

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.

Festergloom

Nonblack creatures get -1/-1 until end of turn.

Blood Price

Look at the top four cards of your library. Put two of them into your hand and the rest on the bottom of your library in any order. You lose 2 life.

Victimize

Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.

Swamp

Swarm of Rats

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

Grandmother Ravi Sengir

Flying
Whenever a creature an opponent controls dies, put a +1/+1 counter on Grandmother Ravi Sengir and you gain 1 life.

Invasion of Ulgrotha

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of Ulgrotha enters, it deals 3 damage to any other target and you gain 3 life.

Invasion of Ulgrotha // Grandmother Ravi Sengir

Karumonix, the Rat King

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Other Rats you control have toxic 1.
When Karumonix enters, 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.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Mirrodin Avenged

Destroy target creature that was dealt damage this turn.
Draw a card.

Crippling Fear

Choose a creature type. Creatures that aren't of the chosen type get -3/-3 until end of turn.

Cremate

Exile target card from a graveyard.
Draw a card.

Vermin Gorger

{T}, Sacrifice another creature: Each opponent loses 2 life and you gain 2 life.

Cast Down

Anoint with Affliction

Exile target creature if it has mana value 3 or less.
Corrupted — Exile that creature instead if its controller has three or more poison counters.

Epicure of Blood

Whenever you gain life, each opponent loses 1 life.

Glistening Deluge

All creatures get -1/-1 until end of turn. Creatures that are green and/or white get an additional -2/-2 until end of turn.

Radiant Fountain

When Radiant Fountain enters, you gain 2 life.
{T}: Add {C}.

Typhoid Rats

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

Altar's Reap

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Cower in Fear

In Garruk's Wake

Destroy all creatures you don't control and all planeswalkers you don't control.

Bitter Revelation

Look at the top four cards of your library. Put two of them into your hand and the rest into your graveyard. You lose 2 life.

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.