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.

Deathsprout

Destroy target creature. Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Mirror Box

The "legend rule" doesn't apply to permanents you control.
Each legendary creature you control gets +1/+1.
Each nontoken creature you control gets +1/+1 for each other creature you control with the same name as that creature.

Songs of the Damned

Add {B} for each creature card in your graveyard.

Haunted One

Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Ashcoat of the Shadow Swarm

Whenever Ashcoat of the Shadow Swarm 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.)

Inga and Esika

Creatures you control have vigilance and "{T}: Add one mana of any color. Spend this mana only to cast a creature spell."
Whenever you cast a creature spell, if three or more mana from creatures was spent to cast it, draw a card.

Ogre Slumlord

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

Cabal Coffers

{2}, {T}: Add {B} for each Swamp you control.

Bojuka Bog

Bojuka Bog enters tapped.
When Bojuka Bog enters, exile target player's graveyard.
{T}: Add {B}.

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Negate

Species Specialist

As Species Specialist enters, choose a creature type.
Whenever a creature of the chosen type dies, you may draw a card.

Path of Ancestry

Path of Ancestry 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.)

Undercity Sewers

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

Rat Colony

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

Phyrexian Tower

{T}: Add {C}.
{T}, Sacrifice a creature: Add {B}{B}.

Damnation

Destroy all creatures. They can't be regenerated.

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Skullclamp

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

Arcane Signet

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

Cryptolith Rite

Creatures you control have "{T}: Add one mana of any color."

Sword of the Squeak

Equipped creature gets +1/+1 for each creature you control with base power or toughness 1.
Whenever a Hamster, Mouse, Rat, or Squirrel you control enters, you may attach Sword of the Squeak to that creature.
Equip {2}

Bloodbond March

Whenever a player casts a creature spell, each player returns all cards with the same name as that spell from their graveyard to the battlefield.

Woodland Chasm

({T}: Add {B} or {G}.)
Woodland Chasm enters tapped.

Liliana of the Dark Realms

+1: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.
−3: Target creature gets +X/+X or -X/-X until end of turn, where X is the number of Swamps you control.
−6: You get an emblem with "Swamps you control have '{T}: Add {B}{B}{B}{B}.'"

Swarmyard

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

Urborg, Tomb of Yawgmoth

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

Syr Konrad, the Grim

Whenever another creature dies, or a creature card is put into a graveyard from anywhere other than the battlefield, or a creature card leaves your graveyard, Syr Konrad, the Grim deals 1 damage to each opponent.
{1}{B}: Each player mills a card. (They each put the top card of their library into their graveyard.)

Patriarch's Bidding

Each player chooses a creature type. Each player returns all creature cards of a type chosen this way from their graveyard to the battlefield.

Putrefy

Destroy target artifact or creature. It can't be regenerated.

Forest

Vanquisher's Banner

As Vanquisher's Banner enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.

Herald's Horn

As Herald's Horn enters, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Twisted Sewer-Witch

When Twisted Sewer-Witch 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 Aura is put into a graveyard, each opponent loses 1 life.)

Kindred Discovery

As Kindred Discovery enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Swamp

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.

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Underground Mortuary

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

Overgrown Tomb

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

Echoing Return

Return target creature card and all other cards with the same name as that card from your graveyard to your hand.

Village Rites

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

Night's Whisper

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Sol Ring

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Cultivate

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 creature can't block."

Realmwalker

Changeling (This card is every creature type.)
As Realmwalker enters, choose a creature type.
You may look at the top card of your library any time.
You may cast creature spells of the chosen type from the top of your library.

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Nashi, Moon's Legacy

Menace, ward {1}
Whenever Nashi, Moon's Legacy attacks, exile up to one target legendary or Rat card from your graveyard and copy it. You may cast the copy. (You still pay its costs. A copy of a permanent spell becomes a token.)

Island

Beast Whisperer

Whenever you cast a creature spell, draw a card.

Whip of Erebos

Creatures you control have lifelink.
{2}{B}{B}, {T}: Return target creature card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step. If it would leave the battlefield, exile it instead of putting it anywhere else. Activate only as a sorcery.

Command Tower

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Garruk's Uprising

When Garruk's Uprising enters, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample.
Whenever a creature you control with power 4 or greater enters, draw a card.