Cairn Wanderer

Changeling (This card is every creature type.)
As long as a creature card with flying is in a graveyard, Cairn Wanderer has flying. The same is true for fear, first strike, double strike, deathtouch, haste, landwalk, lifelink, protection, reach, trample, shroud, and vigilance.

Distorted Curiosity

Corrupted — This spell costs {2} less to cast if an opponent has three or more poison counters.
Draw two cards.

Access Tunnel

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

Dark Impostor

{4}{B}{B}: Exile target creature and put a +1/+1 counter on Dark Impostor.
Dark Impostor has all activated abilities of all creature cards exiled with it.

Experimental Augury

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Universal Automaton

Changeling (This card is every creature type.)

Nekrataal

First strike
When Nekrataal enters the battlefield, destroy target nonartifact, nonblack creature. That creature can't be regenerated.

Slip Through Space

Devoid (This card has no color.)
Target creature can't be blocked this turn.
Draw a card.

Sky Diamond

Sky Diamond enters the battlefield tapped.
{T}: Add {U}.

Pestilent Syphoner

Flying
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)

Key to the City

{T}, Discard a card: Up to one target creature can't be blocked this turn.
Whenever Key to the City becomes untapped, you may pay {2}. If you do, draw a card.

Tsabo's Assassin

{T}: Destroy target creature if it shares a color with the most common color among all permanents or a color tied for most common. A creature destroyed this way can't be regenerated.

Island

Suq'Ata Assassin

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever Suq'Ata Assassin attacks and isn't blocked, defending player gets a poison counter. (A player with ten or more poison counters loses the game.)

Aven Heartstabber

Flying
As long as there are five or more mana values among cards in your graveyard, Aven Heartstabber gets +2/+2 and has deathtouch.
When Aven Heartstabber dies, mill two cards, then draw a card.

Ramses, Assassin Lord

Deathtouch
Other Assassins you control get +1/+1.
Whenever a player loses the game, if they were attacked this turn by an Assassin you controlled, you win the game.

Xathrid Slyblade

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
{3}{B}: Until end of turn, Xathrid Slyblade loses hexproof and gains first strike and deathtouch. (It deals combat damage before creatures without first strike. Any amount of damage it deals to a creature is enough to destroy it.)

Bilious Skulldweller

Deathtouch
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Murder

Mari, the Killing Quill

Whenever a creature an opponent controls dies, exile it with a hit counter on it.
Assassins, Mercenaries, and Rogues you control have deathtouch and "Whenever this creature deals combat damage to a player, you may remove a hit counter from a card that player owns in exile. If you do, draw a card and create two Treasure tokens."

Aqueous Form

Enchant creature
Enchanted creature can't be blocked.
Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Kaito, Dancing Shadow

Whenever one or more creatures you control deal combat damage to a player, you may return one of them to its owner's hand. If you do, you may activate loyalty abilities of Kaito twice this turn rather than only once.
+1: Up to one target creature can't attack or block until your next turn.
0: Draw a card.
−2: Create a 2/2 colorless Drone artifact creature token with deathtouch and "When this creature leaves the battlefield, each opponent loses 2 life and you gain 2 life."

Scarblade Elite

{T}, Exile an Assassin card from your graveyard: Destroy target creature.

Changeling Outcast

Changeling (This card is every creature type.)
Changeling Outcast can't block and can't be blocked.

Go for the Throat

Agent of the Fates

Deathtouch
Heroic — Whenever you cast a spell that targets Agent of the Fates, each opponent sacrifices a creature.

Royal Assassin

Blightbelly Rat

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Blightbelly Rat dies, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Necrogen Communion

Enchant creature you control
Enchanted creature has toxic 2. (Players dealt combat damage by it also get two poison counters.)
When enchanted creature dies, return that card to the battlefield under your control.

Drown in Ichor

Target creature gets -4/-4 until end of turn. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Swamp

Venomous Changeling

Changeling (This card is every creature type.)
Deathtouch

Voidwing Hybrid

Flying
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When you proliferate, return Voidwing Hybrid from your graveyard to your hand.

Phyresis

Enchant creature
Enchanted creature has infect. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Ruthless Ripper

Deathtouch
Morph—Reveal a black card in your hand. (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Ruthless Ripper is turned face up, target player loses 2 life.

Charcoal Diamond

Charcoal Diamond enters the battlefield tapped.
{T}: Add {B}.

Plague Stinger

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

Massacre Girl

Menace
When Massacre Girl enters the battlefield, each other creature gets -1/-1 until end of turn. Whenever a creature dies this turn, each creature other than Massacre Girl gets -1/-1 until end of turn.

Artful Dodge

Target creature can't be blocked this turn.
Flashback {U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Rogue's Passage

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

Termination Facilitator

{T}: Put a bounty counter on target creature or planeswalker. Activate only as a sorcery.
Whenever a creature or planeswalker an opponent controls with a bounty counter on it is dealt damage, destroy it.

Adaptive Automaton

As Adaptive Automaton enters the battlefield, choose a creature type.
Adaptive Automaton is the chosen type in addition to its other types.
Other creatures you control of the chosen type get +1/+1.

Gixian Skullflayer

At the beginning of your upkeep, if there are three or more creature cards in your graveyard, put a +1/+1 counter on Gixian Skullflayer.

Quietus Spike

Equipped creature has deathtouch.
Whenever equipped creature deals combat damage to a player, that player loses half their life, rounded up.
Equip {3}

Bloodline Pretender

Changeling (This card is every creature type.)
As Bloodline Pretender enters the battlefield, choose a creature type.
Whenever another creature of the chosen type enters the battlefield under your control, put a +1/+1 counter on Bloodline Pretender.

Hired Poisoner

Midnight Assassin

Sol Ring

Manifold Key

{1}, {T}: Untap another target artifact.
{3}, {T}: Target creature can't be blocked this turn.

Cut Down

Destroy target creature with total power and toughness 5 or less.

Bojuka Bog

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

Silumgar Assassin

Creatures with power greater than Silumgar Assassin's power can't block it.
Megamorph {2}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)
When Silumgar Assassin is turned face up, destroy target creature with power 3 or less an opponent controls.

Prologue to Phyresis

Each opponent gets a poison counter.
Draw a card.

Sign in Blood

Target player draws two cards and loses 2 life.

Whisper of the Dross

Target creature gets -1/-1 until end of turn. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Prosthetic Injector

Equipped creature gets +0/+2 and has toxic 1. (Players dealt combat damage by equipped creature also get a poison counter.)
Equip {1}

Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Crippling Fear

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

Arcane Signet

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

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Stalking Assassin

{3}{U}, {T}: Tap target creature.
{3}{B}, {T}: Destroy target tapped creature.

Mask of Riddles

Equipped creature has fear. (It can't be blocked except by artifact creatures and/or black creatures.)
Whenever equipped creature deals combat damage to a player, you may draw a card.
Equip {2}

Vraska's Fall

Each opponent sacrifices a creature or planeswalker and gets a poison counter.

Tezzeret's Gambit

({U/P} can be paid with either {U} or 2 life.)
Draw two cards, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Doom Blade

Anoint with Affliction

Exile target creature if it has mana value 3 or less.
Corrupted — Exile that creature instead if its controller has three or more poison counters.

Steady Progress

Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Draw a card.

Contentious Plan

Command Tower

Infectious Inquiry

You draw two cards and you lose 2 life. Each opponent gets a poison counter.

Callidus Assassin

Flash
Polymorphine — You may have Callidus Assassin enter the battlefield tapped as a copy of any creature on the battlefield, except it has "When this creature enters the battlefield, destroy up to one other target creature with the same name as this creature."