Vren, the Relentless

Ward {2}
If a creature an opponent controls would die, exile it instead.
At the beginning of each end step, create X 1/1 black Rat creature tokens with "This token gets +1/+1 for each other Rat you control," where X is the number of creatures that were exiled under your opponents' control this turn.

Rat Colony

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

Mad Ratter

Whenever you draw your second card each turn, create two 1/1 black Rat creature tokens.

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Akoum Teeth

Akoum Warrior

Akoum Warrior // Akoum Teeth

Searstep Pathway

Blightstep Pathway

Blightstep Pathway // Searstep Pathway

Stormcarved Coast

This land enters tapped unless you control two or more other lands.
{T}: Add {U} or {R}.

Plague of Vermin

Starting with you, each player may pay any amount of life. Repeat this process until no one pays life. Each player creates a 1/1 black Rat creature token for each 1 life they paid this way.

Wick, the Whorled Mind

Whenever Wick or another Rat you control enters, create a 1/1 black Snail creature token if you don't control a Snail. Otherwise, put a +1/+1 counter on a Snail you control.
{U}{B}{R}, Sacrifice a Snail: Wick deals damage equal to the sacrificed creature's power to each opponent. Then draw cards equal to the sacrificed creature's power.

Steam Vents

({T}: Add {U} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Gnawing Crescendo

Creatures you control get +2/+0 until end of turn. Whenever a nontoken creature you control dies this turn, create a 1/1 black Rat creature token with "This token can't block."

Rakdos Carnarium

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {B}{R}.

Titan of Littjara

As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
Whenever this creature enters or attacks, you may draw a card for each other creature you control that shares a creature type with it. If you do, discard a card.

Arcane Signet

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

Black Market Connections

At the beginning of your first main phase, choose one or more —
• Sell Contraband — Create a Treasure token. You lose 1 life.
• Buy Information — Draw a card. You lose 2 life.
• Hire a Mercenary — Create a 3/2 colorless Shapeshifter creature token with changeling. You lose 3 life. (It is every creature type.)

Distant Melody

Choose a creature type. Draw a card for each permanent you control of that type.

Murkwater Pathway

Clearwater Pathway

Clearwater Pathway // Murkwater Pathway

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Freya Crescent

Jump — During your turn, Freya Crescent has flying.
{T}: Add {R}. Spend this mana only to cast an Equipment spell or activate an equip ability.

Undercity Sewers

({T}: Add {U} or {B}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Luxury Suite

This land enters tapped unless you have two or more opponents.
{T}: Add {B} or {R}.

Hagra Broodpit

Hagra Mauling

This spell costs {1} less to cast if an opponent controls no basic lands.
Destroy target creature.

Hagra Mauling // Hagra Broodpit

Lord Skitter, Sewer King

Whenever another Rat you control enters, exile up to one target card from an opponent's graveyard.
At the beginning of combat on your turn, create a 1/1 black Rat creature token with "This token can't block."

Sewers of Estark

Choose target creature. If it's attacking, it can't be blocked this turn. If it's blocking, prevent all combat damage that would be dealt this combat by it and each creature it's blocking.

Bojuka Bog

This land enters tapped.
When this land enters, exile target player's graveyard.
{T}: Add {B}.

Path of Ancestry

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Enduring Curiosity

Flash
Whenever a creature you control deals combat damage to a player, draw a card.
When Enduring Curiosity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Murky Sewer

This land enters tapped unless a player has 13 or less life.
{T}: Add {U} or {B}.

Tangled Colony

This creature can't block.
When this creature dies, create X 1/1 black Rat creature tokens with "This token can't block," where X is the amount of damage dealt to it this turn.

Badlands

Ink-Eyes, Servant of Oni

Ninjutsu {3}{B}{B} ({3}{B}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Ink-Eyes deals combat damage to a player, you may put target creature card from that player's graveyard onto the battlefield under your control.
{1}{B}: Regenerate Ink-Eyes.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Sunken Hollow

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

Jwari Ruins

Jwari Disruption

Counter target spell unless its controller pays {1}.

Jwari Disruption // Jwari Ruins

Beyeen Coast

Beyeen Veil

Creatures your opponents control get -2/-0 until end of turn.

Beyeen Veil // Beyeen Coast

Crumbling Necropolis

This land enters tapped.
{T}: Add {U}, {B}, or {R}.

Talisman of Indulgence

{T}: Add {C}.
{T}: Add {B} or {R}. This artifact deals 1 damage to you.

Patchwork Banner

As this artifact enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{T}: Add one mana of any color.

Dimir Aqueduct

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

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.

Mindwhisker

At the beginning of your upkeep, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Threshold — As long as seven or more cards are in your graveyard, creatures your opponents control get -1/-0.

Smoldering Marsh

({T}: Add {B} or {R}.)
This land enters tapped unless you control two or more basic lands.

Terminate

Destroy target creature. It can't be regenerated.

Kazuul's Cliffs

Kazuul's Fury

As an additional cost to cast this spell, sacrifice a creature.
Kazuul's Fury deals damage equal to the sacrificed creature's power to any target.

Kazuul's Fury // Kazuul's Cliffs

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Sol Ring

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Morphic Pool

This land enters tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

Blood Crypt

({T}: Add {B} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

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 this creature.

Reliquary Tower

Sulfur Falls

This land enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Counterspell

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Valley Rotcaller

Menace
Whenever this creature attacks, each opponent loses X life and you gain X life, where X is the number of other Squirrels, Bats, Lizards, and Rats you control.

Swamp

Haunted Ridge

This land enters tapped unless you control two or more other lands.
{T}: Add {B} or {R}.

Command Tower

Temple of Deceit

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {U} or {B}.

Ashcoat of the Shadow Swarm

Whenever Ashcoat attacks or blocks, other Rats you control get +X/+X until end of turn, where X is the number of Rats you control.
At the beginning of your end step, you may mill four cards. If you do, return up to two Rat creature cards from your graveyard to your hand. (To mill a card, put the top card of your library into your graveyard.)

Revenge of the Rats

Create a tapped 1/1 black Rat creature token for each creature card in your graveyard.
Flashback {2}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Malakir Mire

Malakir Rebirth

Choose target creature. You lose 2 life. Until end of turn, that creature gains "When this creature dies, return it to the battlefield tapped under its owner's control."

Malakir Rebirth // Malakir Mire

Reflections of Littjara

As this enchantment enters, choose a creature type.
Whenever you cast a spell of the chosen type, copy that spell. (A copy of a permanent spell becomes a token.)

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.

Dragonskull Summit

This land enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Drainpipe Vermin

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

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Fell Mire

As this land enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {B}.

Fell the Profane

Fell the Profane // Fell Mire

Shipwreck Marsh

This land enters tapped unless you control two or more other lands.
{T}: Add {U} or {B}.

Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Sewer Rats

{B}, Pay 1 life: This creature gets +1/+0 until end of turn. Activate no more than three times each turn.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Drowned Catacomb

This land enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Twisted Sewer-Witch

When this creature enters, create a 1/1 black Rat creature token with "This creature can't block." Then for each Rat you control, create a Wicked Role token attached to that Rat. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1. When this token is put into a graveyard, each opponent loses 1 life.)

Training Center

This land enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Watery Grave

({T}: Add {U} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

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.

Lord Skitter's Butcher

When this creature enters, choose one —
• Create a 1/1 black Rat creature token with "This token can't block."
• You may sacrifice another creature. If you do, scry 2, then draw a card.
• Creatures you control gain menace until end of turn.

Xander's Lounge

({T}: Add {U}, {B}, or {R}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Gix, Yawgmoth Praetor

Whenever a creature deals combat damage to one of your opponents, its controller may pay 1 life. If they do, they draw a card.
{4}{B}{B}{B}, Discard X cards: Exile the top X cards of target opponent's library. You may play lands and cast spells from among cards exiled this way without paying their mana costs.