Paladin of Predation

Toxic 6 (Players dealt combat damage by this creature also get six poison counters.)
Paladin of Predation can't be blocked by creatures with power 2 or less.

Branchblight Stalker

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

Skullpiercer Gnat

Flying
Toxic 1
Whenever Skullpiercer Gnat deals combat damage to a player, a random nonland card in that player's hand perpetually gains "When you cast this spell, you get a poison counter."

Forest

Gate of the Black Dragon

Gate of the Black Dragon enters tapped.
{3}{B}, {T}: Seek a nonland card. Activate only once.
{T}: Add {B}.

Dune Mover

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Dune Mover enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top.

Deathcap Glade

Deathcap Glade enters tapped unless you control two or more other lands.
{T}: Add {B} or {G}.

Plague Nurse

Toxic 2
{2}{G}: Each other creature you control with toxic gains toxic 1 until end of turn. Activate only once each turn. (A player dealt combat damage by a creature with toxic also gets poison counters equal to that creature's total toxic value.)

Sheoldred's Headcleaver

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

Jungle Hollow

Jungle Hollow enters tapped.
When Jungle Hollow enters, you gain 1 life.
{T}: Add {B} or {G}.

Swamp

Venerated Rotpriest

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Whenever a creature you control becomes the target of a spell, target opponent gets a poison counter.

Viral Spawning

Create a 3/3 green Phyrexian Beast creature token with toxic 1. (Players dealt combat damage by it also get a poison counter.)
Corrupted — As long as an opponent has three or more poison counters and Viral Spawning is in your graveyard, it has flashback {2}{G}. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

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.)

Bilious Skulldweller

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

Hero's Downfall

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.)

Gate to Manorborn

Gate to Manorborn enters the battlefield tapped.
{3}{G}, {T}: Seek a nonland card. Activate only once.
{T}: Add {G}.

Stinging Hivemaster

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

Haunted Mire

({T}: Add {B} or {G}.)
Haunted Mire enters tapped.

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.

Glissa Sunslayer

First strike, deathtouch
Whenever Glissa Sunslayer deals combat damage to a player, choose one —
• You draw a card and you lose 1 life.
• Destroy target enchantment.
• Remove up to three counters from target permanent.

Pestilent Syphoner

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