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.)

Prologue to Phyresis

Each opponent gets a poison counter.
Draw a card.

Scheming Aspirant

Whenever you proliferate, each opponent loses 2 life and you gain 2 life.

Crawling Chorus

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Crawling Chorus dies, create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block."

Rustvine Cultivator

{T}: Put an oil counter on Rustvine Cultivator.
{T}, Remove an oil counter from Rustvine Cultivator: Untap target land.

Basilica Skullbomb

{1}, Sacrifice Basilica Skullbomb: Draw a card.
{2}{W}, Sacrifice Basilica Skullbomb: Target creature you control gets +2/+2 and gains flying until end of turn. Draw a card. Activate only as a sorcery.

Cutthroat Centurion

Sacrifice another artifact or creature: Cutthroat Centurion gets +2/+2 until end of turn. Activate only once each turn.

Forest

Necrogen Rotpriest

Toxic 2 (Players dealt combat damage by this creature also get two poison counters.)
Whenever a creature you control with toxic deals combat damage to a player, that player gets an additional poison counter.
{1}{B}{G}: Target creature you control with toxic gains deathtouch until end of turn.

Bonepicker Skirge

Flying
Corrupted — As long as an opponent has three or more poison counters, Bonepicker Skirge has deathtouch and lifelink.

Myr Convert

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
{T}, Pay 2 life: Add one mana of any color.

Meldweb Strider

Vigilance
Meldweb Strider enters with an oil counter on it.
Remove an oil counter from Meldweb Strider: It becomes an artifact creature until end of turn.
Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.)

Titanic Growth

Target creature gets +4/+4 until end of turn.

Vat of Rebirth

Whenever another artifact or creature you control is put into a graveyard from the battlefield, put an oil counter on Vat of Rebirth.
{2}{B}, {T}, Remove four oil counters from Vat of Rebirth: Return target creature card from your graveyard to the battlefield. Activate only as a sorcery.

Bilious Skulldweller

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

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

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.

Feed the Infection

You draw three cards and you lose 3 life.
Corrupted — Each opponent who has three or more poison counters loses 3 life.

Maze Skullbomb

{1}, Sacrifice Maze Skullbomb: Draw a card.
{2}{G}, Sacrifice Maze Skullbomb: Target creature you control gets +3/+3 and gains trample until end of turn. Draw a card. Activate only as a sorcery.

Fleshless Gladiator

Corrupted — {2}{B}: Return Fleshless Gladiator from your graveyard to the battlefield tapped. You lose 1 life. Activate only if an opponent has three or more poison counters.

Myr Custodian

When Myr Custodian enters, scry 2. Then each opponent may scry 1. (To scry X, a player looks at the top X cards of their library, then puts any number of them on the bottom and the rest on top in any order.)

Nimraiser Paladin

Toxic 2 (Players dealt combat damage by this creature also get two poison counters.)
When Nimraiser Paladin enters, return target creature card with mana value 3 or less from your graveyard to your hand.

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}

Darkslick Shores

Darkslick Shores enters tapped unless you control two or fewer other lands.
{T}: Add {U} or {B}.

Ichorspit Basilisk

Sheoldred's Headcleaver

Menace
Toxic 2 (Players dealt combat damage by this creature also get two poison counters.)

Surgical Skullbomb

{1}, Sacrifice Surgical Skullbomb: Draw a card.
{2}{U}, Sacrifice Surgical Skullbomb: Return target creature to its owner's hand. Draw a card. Activate only as a sorcery.

Plains

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.)

Ichor Synthesizer

Whenever you cast a noncreature spell, put an oil counter on Ichor Synthesizer.
As long as Ichor Synthesizer has four or more oil counters on it, it gets +2/+0 and can't be blocked.

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.

Vat Emergence

Put target creature card from a graveyard onto the battlefield under your control. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cruel Grimnarch

Deathtouch
When Cruel Grimnarch enters, each opponent discards a card. For each opponent who can't, you gain 4 life.

Encroaching Mycosynth

Nonland permanents you control are artifacts in addition to their other types. The same is true for permanent spells you control and nonland permanent cards you own that aren't on the battlefield.

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.)

Gitaxian Anatomist

When Gitaxian Anatomist enters, you may tap it. If you do, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Expand the Sphere

Look at the top six cards of your library. Put up to two land cards from among them onto the battlefield tapped and the rest on the bottom of your library in a random order. If you put fewer than two lands onto the battlefield this way, proliferate a number of times equal to the difference. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Swamp

Malcator's Watcher

Flying, vigilance
When Malcator's Watcher dies, draw a card.

Compleat Devotion

Target creature you control gets +2/+2 until end of turn. If that creature has toxic, draw a card.