Whenever Ayara, First of Locthwain or another black creature enters the battlefield under your control, each opponent loses 1 life and you gain 1 life.

{T}, Sacrifice another black creature: Draw a card.

Whenever a creature dies, put a charge counter on Black Market.

At the beginning of your precombat main phase, add {B} for each charge counter on Black Market.

Bojuka Bog enters the battlefield tapped.

When Bojuka Bog enters the battlefield, exile target player's graveyard.

{T}: Add {B}.

When Burglar Rat enters the battlefield, each opponent discards a card.

As Caged Sun enters the battlefield, choose a color.

Creatures you control of the chosen color get +1/+1.

Whenever a land's ability causes you to add one or more mana of the chosen color, add one additional mana of that color.

{3}{B}{B}, {T}, Sacrifice X other creatures: Return X target creature cards from your graveyard to the battlefield.

{5}{B}{B}: Put Champion of Stray Souls on top of your library from your graveyard.

Charcoal Diamond enters the battlefield tapped.

{T}: Add {B}.

Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)

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

Equipped creature gets +3/+3 and has protection from each color that's not in your commander's color identity.

Equip commander {3}

Equip {5}

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

Add {B}{B}{B}.

Flying

When Death's-Head Buzzard dies, all creatures get -1/-1 until end of turn.

Whenever another creature dies, you may gain 1 life.

Search your library for a card, put that card into your hand, then shuffle.

When Dire Fleet Hoarder dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

{B}, Discard a card: Regenerate Dirty Wererat.

Threshold -- As long as seven or more cards are in your graveyard, Dirty Wererat gets +2/+2 and can't block.

When Earsplitting Rats enters the battlefield, each player discards a card.

Discard a card: Regenerate Earsplitting Rats.

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.)

Flying

Devour 2 (As this enters the battlefield, you may sacrifice any number of creatures. This creature enters the battlefield with twice that many +1/+1 counters on it.)

Destroy target creature or planeswalker.

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

Equipped creature gets +1/+1.

Whenever equipped creature deals combat damage to a player, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

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

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

All creatures get -X/-X until end of turn, where X is the sacrificed creature's power.

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

When Ichor Rats enters the battlefield, each player gets a poison counter.

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, Servant of Oni 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.

Choose a creature type. Destroy all creatures that aren't of the chosen type.

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)

{1}{B}: Regenerate Kuro's Taken.

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.

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

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.

Memorial to Folly enters the battlefield tapped.

{T}: Add {B}.

{2}{B}, {T}, Sacrifice Memorial to Folly: Return target creature card from your graveyard to your hand.

When Midnight Scavengers enters the battlefield, you may return target creature card with mana value 3 or less from your graveyard to your hand.

(Melds with Graf Rats.)

Destroy target creature.

{T}: Add {C}.

{4}, {T}: Exile target attacking creature an opponent controls. At the beginning of the next end step, return it to the battlefield tapped under its owner's control.

Nevinyrral's Disk enters the battlefield tapped.

{1}, {T}: Destroy all artifacts, creatures, and enchantments.

{B}, Sacrifice a creature: Target player discards a card. Activate only as a sorcery.

{4}, {T}: Put a fate counter on target permanent.

{5}, {T}, Sacrifice Oblivion Stone: Destroy each nonland permanent without a fate counter on it, then remove all fate counters from all permanents.

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

Rats you control have deathtouch.

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.

Path of Ancestry enters the battlefield 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.)

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.)

{T}: Add {C}.

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

{2}, {T}, Sacrifice a creature: Draw a card.

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.

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

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.

Flying

{1}, Sacrifice another creature: Put a +1/+1 counter on Ravenous Harpy.

When Ravenous Rats enters the battlefield, target opponent discards a card.

Scry 2, then draw two cards. You lose 2 life.

Return target creature card from your graveyard to your hand.

Draw a card.

{T}: Add {C}.

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

Deathtouch

When Ruin Rat dies, exile target card from an opponent's graveyard.

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.

At the beginning of your upkeep or whenever you cast a black spell, put a charge counter on Shrine of Limitless Power.

{4}, {T}, Sacrifice Shrine of Limitless Power: Target player discards a card for each charge counter on Shrine of Limitless Power.

Flying

Exploit (When this creature enters the battlefield, you may sacrifice a creature.)

Whenever another creature you control dies, put a +1/+1 counter on Silumgar Scavenger. It gains haste until end of turn if it exploited that creature.

{T}: Add {C}{C}.

As Species Specialist enters the battlefield, choose a creature type.

Whenever a creature of the chosen type dies, you may draw a card.

Swallowing Plague deals X damage to target creature and you gain X life.

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

({T}: Add {B}.)

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

{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.)

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

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.)

You have no maximum hand size.

{T}: Add {C}.

{1}, Sacrifice Traveler's Amulet: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.

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

{7}, {T}, Sacrifice Universal Solvent: Destroy target permanent.

{T}: Add {C}.

{7}, {T}, Sacrifice Unstable Obelisk: Destroy target permanent.

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

Draw two cards.

Return up to two target creature cards from your graveyard to your hand.

Cycling {2} ({2}, Discard this card: Draw a card.)

{T}: Add {C}.

{3}, {T}, Pay life equal to the number of colors in your commanders' color identity: Draw a card.

{1}{B}, {T}, Sacrifice a creature: You gain 1 life and draw a card.

({T}: Add {B}.)

Witch's Cottage enters the battlefield tapped unless you control three or more other Swamps.

When Witch's Cottage enters the battlefield untapped, you may put target creature card from your graveyard on top of your library.

When Zhalfirin Void enters the battlefield, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

{T}: Add {C}.

Whenever Zulaport Cutthroat or another creature you control dies, each opponent loses 1 life and you gain 1 life.