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.)

Altar of the Brood

Whenever another permanent enters the battlefield under your control, each opponent mills a card.

Stabwhisker the Odious

At the beginning of each opponent's upkeep, that player loses 1 life for each card fewer than three in their hand.

Nezumi Shortfang

{1}{B}, {T}: Target opponent discards a card. Then if that player has no cards in hand, flip Nezumi Shortfang.

Nezumi Shortfang // Stabwhisker the Odious

Gravepurge

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

Thrumming Stone

Spells you cast have ripple 4. (Whenever you cast a spell, you may reveal the top four cards of your library. You may cast spells with the same name as that spell from among the revealed cards without paying their mana costs. Put the rest on the bottom of your library.)

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

Bojuka Bog

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

The Meathook Massacre

When The Meathook Massacre enters the battlefield, each creature gets -X/-X until end of turn.
Whenever a creature you control dies, each opponent loses 1 life.
Whenever a creature an opponent controls dies, you gain 1 life.

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.

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.

Phyrexian Altar

Sacrifice a creature: Add one mana of any color.

Species Specialist

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

Diabolic Intent

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a card, put that card into your hand, then shuffle.

Thornbite Staff

Equipped creature has "{2}, {T}: This creature deals 1 damage to any target" and "Whenever a creature dies, untap this creature."
Whenever a Shaman creature enters the battlefield, you may attach Thornbite Staff to it.
Equip {4}

Sword of the Paruns

As long as equipped creature is tapped, tapped creatures you control get +2/+0.
As long as equipped creature is untapped, untapped creatures you control get +0/+2.
{3}: You may tap or untap equipped creature.
Equip {3}

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.)

Umbral Mantle

Equipped creature has "{3}, {Q}: This creature gets +2/+2 until end of turn." ({Q} is the untap symbol.)
Equip {0}

Phyrexian Reclamation

{1}{B}, Pay 2 life: Return target creature card from your graveyard to your hand.

Thousand-Year Elixir

You may activate abilities of creatures you control as though those creatures had haste.
{1}, {T}: Untap target creature.

Nezumi Bone-Reader

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

Magewright's Stone

{1}, {T}: Untap target creature that has an activated ability with {T} in its cost.

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.

Sol Ring

Dictate of Erebos

Flash
Whenever a creature you control dies, each opponent sacrifices a creature.

Culling the Weak

As an additional cost to cast this spell, sacrifice a creature.
Add {B}{B}{B}{B}.

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Nighteyes the Desecrator

{4}{B}: Put target creature card from a graveyard onto the battlefield under your control.

Nezumi Graverobber

{1}{B}: Exile target card from an opponent's graveyard. If no cards are in that graveyard, flip Nezumi Graverobber.

Nezumi Graverobber // Nighteyes the Desecrator

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.

Ogre Slumlord

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

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.)

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature.

Dark Ritual

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 the battlefield, 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.

Diabolic Tutor

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

Rat Colony

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

Patriar's Seal

{T}: Add one mana of any color.
{1}, {T}: Untap target legendary creature you control.

Flay Essence

Exile target creature or planeswalker. You gain life equal to the number of counters on it.

Swamp

Ayara, First of Locthwain

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.