Ambulatory Edifice

When Ambulatory Edifice enters, you may pay 2 life. When you do, target creature gets -1/-1 until end of turn.

Black Sun's Twilight

Up to one target creature gets -X/-X until end of turn. If X is 5 or more, return a creature card with mana value X or less from your graveyard to the battlefield tapped.

Swamp

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.

Corruption

Bonepicker Skirge

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

Pestilent Syphoner

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

Kinzu of the Bleak Coven

Flying
Whenever another nontoken creature you control dies, you may pay 2 life and exile it. If you do, create a token that's a copy of that creature, except it's 1/1 and has toxic 1. (Players dealt combat damage by it also get a poison counter.)

The Dross Pits

The Dross Pits enters tapped.
{T}: Add {B}.
{1}{B}, {T}, Sacrifice The Dross Pits: Draw a card.

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.)

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.

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.

Annihilating Glare

As an additional cost to cast this spell, pay {4} or sacrifice an artifact or creature.
Destroy target creature or planeswalker.

Dross Skullbomb

{1}, Sacrifice Dross Skullbomb: Draw a card.
{2}{B}, Sacrifice Dross Skullbomb: Return target creature card from your graveyard to your hand. Draw a card. Activate only as a sorcery.

Testament Bearer

When Testament Bearer dies, look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.