Swamp

Scheming Aspirant

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

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.)

Tekuthal, Inquiry Dominus

Flying
If you would proliferate, proliferate twice instead.
{1}{U/P}{U/P}, Remove three counters from among other artifacts, creatures, and planeswalkers you control: Put an indestructible counter on Tekuthal, Inquiry Dominus. ({U/P} can be paid with either {U} or 2 life.)

Mesmerizing Dose

Enchant creature
When Mesmerizing Dose enters, tap enchanted creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Enchanted creature doesn't untap during its controller's untap step.

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}

Glistener Seer

Glistener Seer enters with three oil counters on it.
{T}, Remove an oil counter from Glistener Seer: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

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.

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.

Sheoldred's Headcleaver

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

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.

Island

Darkslick Shores

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

Bring the Ending

Counter target spell unless its controller pays {2}.
Corrupted — Counter that spell instead if its controller has three or more poison counters.

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.)

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.)

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.)

Tamiyo's Immobilizer

Tamiyo's Immobilizer enters with four oil counters on it.
{T}, Remove an oil counter from Tamiyo's Immobilizer: Tap target artifact or creature.