Skrelv's Hive

At the beginning of your upkeep, you lose 1 life and create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block."
Corrupted — As long as an opponent has three or more poison counters, creatures you control with toxic have lifelink.

No More Lies

Counter target spell unless its controller pays {3}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

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.

Plains

Skrelv, Defector Mite

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Skrelv, Defector Mite can't block.
{W/P}, {T}: Choose a color. Another target creature you control gains toxic 1 and hexproof from that color until end of turn. It can't be blocked by creatures of that color this turn. ({W/P} can be paid with either {W} or 2 life.)

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.

Jawbone Duelist

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

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.)

Mirrex

{T}: Add {C}.
{T}: Add one mana of any color. Activate only if Mirrex entered this turn.
{3}, {T}: Create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block." (Players dealt combat damage by it also get a poison counter.)

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."

Tocasia's Welcome

Whenever one or more creatures you control with mana value 3 or less enter, draw a card. This ability triggers only once each turn.

Into the Flood Maw

Gift a tapped Fish (You may promise an opponent a gift as you cast this spell. If you do, they create a tapped 1/1 blue Fish creature token before its other effects.)
Return target creature an opponent controls to its owner's hand. If the gift was promised, instead return target nonland permanent an opponent controls to its owner's hand.

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.

Elspeth's Smite

Elspeth's Smite deals 3 damage to target attacking or blocking creature. If that creature would die this turn, exile it instead.

Serum Snare

Return target nonland permanent to its owner's hand. If that permanent had mana value 3 or less, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Annex Sentry

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Annex Sentry enters, exile target artifact or creature an opponent controls with mana value 3 or less until Annex Sentry leaves the battlefield.

Adarkar Wastes

{T}: Add {C}.
{T}: Add {W} or {U}. Adarkar Wastes deals 1 damage to you.

Island

Doorkeeper Thrull

Flash
Flying
Artifacts and creatures entering don't cause abilities to trigger.

Innkeeper's Talent

(Gain the next level as a sorcery to add its ability.)
At the beginning of combat on your turn, put a +1/+1 counter on target creature you control.
{G}: Level 2
Permanents you control with counters on them have ward {1}.
{3}{G}: Level 3
If you would put one or more counters on a permanent or player, put twice that many of each of those kinds of counters on that permanent or player instead.

Pick Your Poison

Choose one —
• Each opponent sacrifices an artifact of their choice.
• Each opponent sacrifices an enchantment of their choice.
• Each opponent sacrifices a creature with flying of their choice.

Mockingbird

Flying
You may have Mockingbird enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast Mockingbird, except it's a Bird in addition to its other types and it has flying.

The Seedcore

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast Phyrexian creature spells.
Corrupted — {T}: Target 1/1 creature gets +2/+1 until end of turn. Activate only if an opponent has three or more poison counters.

Seachrome Coast

Seachrome Coast enters tapped unless you control two or fewer other lands.
{T}: Add {W} or {U}.

Razorverge Thicket

Razorverge Thicket enters tapped unless you control two or fewer other lands.
{T}: Add {G} or {W}.

Three Tree City

As Three Tree City enters, choose a creature type.
{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to the number of creatures you control of the chosen type.