Toxrill, the Corrosive

At the beginning of each end step, put a slime counter on each creature you don't control.
Creatures you don't control get -1/-1 for each slime counter on them.
Whenever a creature you don't control with a slime counter on it dies, create a 1/1 black Slug creature token.
{U}{B}, Sacrifice a Slug: Draw a card.

Dimir Signet

Slaughter Specialist

When Slaughter Specialist enters, each opponent creates a 1/1 white Human creature token.
Whenever a creature an opponent controls dies, put a +1/+1 counter on Slaughter Specialist.

Mystic Confluence

Choose three. You may choose the same mode more than once.
• Counter target spell unless its controller pays {3}.
• Return target creature to its owner's hand.
• Draw a card.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Filth

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
As long as Filth is in your graveyard and you control a Swamp, creatures you control have swampwalk.

The Myriad Pools

(Transforms from The Everflowing Well.)
{T}: Add {U}.
Whenever you cast a permanent spell using mana produced by The Myriad Pools, up to one other target permanent you control becomes a copy of that spell until end of turn.

The Everflowing Well

When The Everflowing Well enters, mill two cards, then draw two cards.
Descend 8 — At the beginning of your upkeep, if there are eight or more permanent cards in your graveyard, transform The Everflowing Well.

The Everflowing Well // The Myriad Pools

Command Tower

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

Sign in Blood

Target player draws two cards and loses 2 life.

Mana Drain

Counter target spell. At the beginning of your next main phase, add an amount of {C} equal to that spell's mana value.

Sakashima's Student

Ninjutsu {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
You may have Sakashima's Student enter as a copy of any creature on the battlefield, except it's a Ninja in addition to its other creature types.

Teferi's Ageless Insight

If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

Submerged Boneyard

Submerged Boneyard enters tapped.
{T}: Add {U} or {B}.

Blur

Exile target creature you control, then return that card to the battlefield under its owner's control.
Draw a card.

Suppress

Target player exiles all cards from their hand face down. At the beginning of the end step of that player's next turn, that player returns those cards to their hand.

Sublime Epiphany

Choose one or more —
• Counter target spell.
• Counter target activated or triggered ability.
• Return target nonland permanent to its owner's hand.
• Create a token that's a copy of target creature you control.
• Target player draws a card.

Bad River

Bad River enters tapped.
{T}, Sacrifice Bad River: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Twincast

Copy target instant or sorcery spell. You may choose new targets for the copy.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Cabal Stronghold

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

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Leyline of Anticipation

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Forbidden Orchard

{T}: Add one mana of any color.
Whenever you tap Forbidden Orchard for mana, target opponent creates a 1/1 colorless Spirit creature token.

Demonic Tutor

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

Kels, Fight Fixer

Menace
Whenever you sacrifice a creature, you may pay {U/B}. If you do, draw a card. ({U/B} can be paid with either {U} or {B}.)
{1}, Sacrifice a creature: Kels, Fight Fixer gains indestructible until end of turn.

Reliquary Tower

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

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Robe of Mirrors

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has shroud. (It can't be the target of spells or abilities.)

Hunted Phantasm

Hunted Phantasm can't be blocked.
When Hunted Phantasm enters, target opponent creates five 1/1 red Goblin creature tokens.

Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Revel in Riches

Whenever a creature an opponent controls dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
At the beginning of your upkeep, if you control ten or more Treasures, you win the game.

Swamp

Arcane Signet

Genesis Chamber

Whenever a nontoken creature enters, if Genesis Chamber is untapped, that creature's controller creates a 1/1 colorless Myr artifact creature token.

Deepglow Skate

When Deepglow Skate enters, double the number of each kind of counter on any number of target permanents.

Massacre Girl, Known Killer

Menace
Creatures you control have wither. (They deal damage to creatures in the form of -1/-1 counters.)
Whenever a creature an opponent controls dies, if its toughness was less than 1, draw a card.

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

Morphic Pool

Morphic Pool enters tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Castle Vantress

Castle Vantress enters tapped unless you control an Island.
{T}: Add {U}.
{2}{U}{U}, {T}: Scry 2.

Vela the Night-Clad

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)
Other creatures you control have intimidate.
Whenever Vela the Night-Clad or another creature you control leaves the battlefield, each opponent loses 1 life.

Jet Medallion

Black spells you cast cost {1} less to cast.

Kormus Bell

All Swamps are 1/1 black creatures that are still lands.

Cabal Coffers

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

Sol Ring

Infernal Genesis

At the beginning of each player's upkeep, that player mills a card. Then they create X 1/1 black Minion creature tokens, where X is the milled card's mana value.

Island

Massacre Wurm

When this creature enters, creatures your opponents control get -2/-2 until end of turn.
Whenever a creature an opponent controls dies, that player loses 2 life.

Narset's Reversal

Copy target instant or sorcery spell, then return it to its owner's hand. You may choose new targets for the copy.

Nascent Metamorph

Whenever Nascent Metamorph attacks or blocks, target opponent reveals cards from the top of their library until they reveal a creature card. Nascent Metamorph becomes a copy of that card until end of turn. Then that player puts all cards revealed this way on the bottom of their library in a random order.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Yahenni, Undying Partisan

Haste
Whenever a creature an opponent controls dies, put a +1/+1 counter on Yahenni, Undying Partisan.
Sacrifice another creature: Yahenni gains indestructible until end of turn.

Perplexing Test

Choose one —
• Return all creature tokens to their owners' hands.
• Return all nontoken creatures to their owners' hands.

Access Tunnel

{T}: Add {C}.
{3}, {T}: Target creature with power 3 or less can't be blocked this turn.

Blood Money

Destroy all creatures. For each nontoken creature destroyed this way, you create a tapped Treasure token.

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

The Meathook Massacre

When The Meathook Massacre enters, 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.

Gather Specimens

If a creature would enter the battlefield under an opponent's control this turn, it enters under your control instead.

Hunted Horror

Trample
When Hunted Horror enters, target opponent creates two 3/3 green Centaur creature tokens with protection from black.

Rise of the Dark Realms

Put all creature cards from all graveyards onto the battlefield under your control.

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.

Polymorphist's Jest

Until end of turn, each creature target player controls loses all abilities and becomes a blue Frog with base power and toughness 1/1.

Thran Dynamo

Mind Funeral

Target opponent reveals cards from the top of their library until four land cards are revealed. That player puts all cards revealed this way into their graveyard.

Vedalken Orrery

You may cast spells as though they had flash.

Takenuma, Abandoned Mire

{T}: Add {B}.
Channel — {3}{B}, Discard Takenuma, Abandoned Mire: Mill three cards, then return a creature or planeswalker card from your graveyard to your hand. This ability costs {1} less to activate for each legendary creature you control.

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Urborg, Tomb of Yawgmoth

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

Geode Golem

Trample
Whenever Geode Golem deals combat damage to a player, you may cast your commander from the command zone without paying its mana cost. (You still pay any additional costs.)

Shipwreck Marsh

Shipwreck Marsh enters tapped unless you control two or more other lands.
{T}: Add {U} or {B}.

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Snap

Return target creature to its owner's hand. Untap up to two lands.

Cancel

Temple of Deceit

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {U} or {B}.

Hunted Bonebrute

Menace
When Hunted Bonebrute enters, target opponent creates two 1/1 white Dog creature tokens.
When Hunted Bonebrute dies, each opponent loses 3 life.
Disguise {1}{B}

Choked Estuary

As Choked Estuary enters, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters tapped.
{T}: Add {U} or {B}.

Access Denied

Counter target spell. Create X 1/1 colorless Thopter artifact creature tokens with flying, where X is that spell's mana value.

Karn's Temporal Sundering

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Target player takes an extra turn after this one. Return up to one target nonland permanent to its owner's hand. Exile Karn's Temporal Sundering.

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice Ghost Quarter: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Grave Betrayal

Whenever a creature you don't control dies, return it to the battlefield under your control with an additional +1/+1 counter on it at the beginning of the next end step. That creature is a black Zombie in addition to its other colors and types.