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.

Reliquary Tower

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

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.

Read the Bones

Scry 2, then draw two cards. You lose 2 life. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Crippling Fear

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

Crypt of Agadeem

Crypt of Agadeem enters tapped.
{T}: Add {B}.
{2}, {T}: Add {B} for each black creature card in your graveyard.

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.)

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.

Castle Locthwain

Castle Locthwain enters tapped unless you control a Swamp.
{T}: Add {B}.
{1}{B}{B}, {T}: Draw a card, then you lose life equal to the number of cards in your hand.

Phyrexian Arena

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

Ogre Slumlord

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

Crypt Rats

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

Barren Moor

Barren Moor enters tapped.
{T}: Add {B}.
Cycling {B} ({B}, Discard this card: Draw a card.)

Chittering Witch

When Chittering Witch enters, create a number of 1/1 black Rat creature tokens equal to the number of opponents you have.
{1}{B}, Sacrifice a creature: Target creature gets -2/-2 until end of turn.

Village Rites

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

Sign in Blood

Target player draws two cards and loses 2 life.

Cabal Stronghold

{T}: Add {C}.
{3}, {T}: Add {B} for each basic Swamp you control.

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.

Bad Moon

Rat Colony

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

Gravestorm

At the beginning of your upkeep, target opponent may exile a card from their graveyard. If that player doesn't, you may draw a card.

Return from Extinction

Choose one —
• Return target creature card from your graveyard to your hand.
• Return two target creature cards that share a creature type from your graveyard to your hand.