Precipitous Drop

Enchant creature
When this Aura enters, venture into the dungeon. (Enter the first room or advance to the next room.)
Enchanted creature gets -2/-2. It gets -5/-5 instead as long as you've completed a dungeon.

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.

Crown of Suspicion

Enchant creature
Enchanted creature gets +2/-1.
Sacrifice this Aura: Enchanted creature and other creatures that share a creature type with it get +2/-1 until end of turn.

Midnight Scavengers

When this creature enters, you may return target creature card with mana value 3 or less from your graveyard to your hand.
(Melds with Graf Rats.)

Crypt Rats

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

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.)

Swamp

Yuan-Ti Fang-Blade

Deathtouch
Whenever this creature deals combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Murder

Relentless Rats

This creature gets +1/+1 for each other creature on the battlefield named Relentless Rats.
A deck can have any number of cards named Relentless Rats.

Go for the Throat

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

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.)

Rat Colony

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

Graf Rats

At the beginning of combat on your turn, if you both own and control this creature and a creature named Midnight Scavengers, exile them, then meld them into Chittering Host.

Songs of the Damned

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

Gnat Miser

Each opponent's maximum hand size is reduced by one.

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.

Psychic Whorl

Target opponent discards two cards. Then if you control a Rat, surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Dark Ritual

Cast Down

Echoing Return

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

Asphyxiate

Thorn of the Black Rose

Deathtouch
When this creature enters, you become the monarch.

Vicious Battlerager

When this creature enters, you take the initiative.
Spiked Retribution — Whenever this creature becomes blocked by a creature, that creature's controller loses 5 life.

Gray Merchant of Asphodel

When this creature enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Footbottom Feast

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

Pack's Disdain

Choose a creature type. Target creature gets -1/-1 until end of turn for each permanent of the chosen type you control.

Overwhelming Remorse

This spell costs {1} less to cast for each creature card in your graveyard.
Exile target creature or planeswalker.

Dark Bargain

Look at the top three cards of your library. Put two of them into your hand and the other into your graveyard. Dark Bargain deals 2 damage to you.

Swarm of Rats

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

Voracious Vermin

When this creature enters, create a 1/1 black Rat creature token with "This token can't block."
Whenever another creature you control dies, put a +1/+1 counter on this creature.

Rat Out

Up to one target creature gets -1/-1 until end of turn. You create a 1/1 black Rat creature token with "This token can't block."

Chittering Host

Haste
Menace (This creature can't be blocked except by two or more creatures.)
When this creature enters, other creatures you control get +1/+0 and gain menace until end of turn.

Zombie Ogre

At the beginning of your end step, if a creature died this turn, venture into the dungeon. (Enter the first room or advance to the next room.)

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.)

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.)

Raise the Draugr

Gravepurge

Witch's Cottage

({T}: Add {B}.)
This land enters tapped unless you control three or more other Swamps.
When this land enters untapped, you may put target creature card from your graveyard on top of your library.

Syphon Mind

Each other player discards a card. You draw a card for each card discarded this way.

Pestilence

At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.
{B}: This enchantment deals 1 damage to each creature and each player.

Bubbling Muck

Until end of turn, whenever a player taps a Swamp for mana, that player adds an additional {B}.