Ixhel, Scion of Atraxa

Flying, vigilance, toxic 2
Corrupted — At the beginning of your end step, each opponent who has three or more poison counters exiles the top card of their library face down. You may look at and play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast those spells.

Birds of Paradise

Infectious Inquiry

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

Phyresis Outbreak

Each opponent gets a poison counter. Then each creature your opponents control gets -1/-1 until end of turn for each poison counter its controller has.

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.)

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.)

Norn's Decree

Whenever one or more creatures an opponent controls deal combat damage to you, that opponent gets a poison counter.
Whenever a player attacks, if one or more players being attacked are poisoned, the attacking player draws a card.

Phyrexian Censor

Each player can't cast more than one non-Phyrexian spell each turn.
Non-Phyrexian creatures enter tapped.

Swamp

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Unnatural Restoration

Return target permanent card from your graveyard to your hand. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Ichor Rats

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, each player gets a poison counter.

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.)

Infectious Bite

Target creature you control deals damage equal to its power to target creature you don't control. Each opponent gets a poison counter.

Vraska, Betrayal's Sting

Compleated ({B/P} can be paid with {B} or 2 life. If life was paid, this planeswalker enters with two fewer loyalty counters.)
0: You draw a card and you lose 1 life. Proliferate.
−2: Target creature becomes a Treasure artifact with "{T}, Sacrifice this artifact: Add one mana of any color" and loses all other card types and abilities.
−9: If target player has fewer than nine poison counters, they get a number of poison counters equal to the difference.

Viridian Corrupter

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
When Viridian Corrupter enters, destroy target artifact.

Glistening Sphere

Glistening Sphere enters tapped.
When Glistening Sphere enters, proliferate.
{T}: Add one mana of any color.
Corrupted — {T}: Add three mana of any one color. Activate only if an opponent has three or more poison counters.

Worldknit

(Start the game with this conspiracy face up in the command zone.)
As long as every card in your card pool started the game in your library or in the command zone, lands you control have "{T}: Add one mana of any color."

Cankerbloom

{1}, Sacrifice Cankerbloom: Choose one —
• Destroy target artifact.
• Destroy target enchantment.
• Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Grafted Butcher

When Grafted Butcher enters, Phyrexians you control gain menace until end of turn.
Other Phyrexians you control get +1/+1.
{3}{B}, Sacrifice an artifact or creature: Return Grafted Butcher from your graveyard to the battlefield. Activate only as a sorcery.

Dirge of Dread

All creatures gain fear until end of turn. (They can't be blocked except by artifact creatures and/or black creatures.)
Cycling {1}{B} ({1}{B}, Discard this card: Draw a card.)
When you cycle Dirge of Dread, you may have target creature gain fear until end of turn.