Fungal Infection

Target creature gets -1/-1 until end of turn. Create a 1/1 green Saproling creature token.

Swamp

Zombie Infestation

Discard two cards: Create a 2/2 black Zombie creature token.

Faith of the Devoted

Whenever you cycle or discard a card, you may pay {1}. If you do, each opponent loses 2 life and you gain 2 life.

Shambling Ghast

When Shambling Ghast dies, choose one —
• Target creature an opponent controls gets -1/-1 until end of turn.
• Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Penregon Besieged

At the beginning of your end step, choose a creature with the least toughness among creatures your opponents control. It perpetually gets -1/-1.
When your opponents control no creatures, sacrifice Penregon Besieged.

Archfiend of Ifnir

Flying
Whenever you cycle or discard another card, put a -1/-1 counter on each creature your opponents control.
Cycling {2} ({2}, Discard this card: Draw a card.)

Bag of Holding

Whenever you discard a card, exile that card from your graveyard.
{2}, {T}: Draw a card, then discard a card.
{4}, {T}, Sacrifice Bag of Holding: Return all cards exiled with Bag of Holding to their owner's hand.

Foreboding Fruit

Target player draws two cards and loses 2 life.
Adamant — If at least three black mana was spent to cast this spell, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

Nest of Scarabs

Whenever you put one or more -1/-1 counters on a creature, create that many 1/1 black Insect creature tokens.

Ruthless Sniper

Whenever you cycle or discard a card, you may pay {1}. If you do, put a -1/-1 counter on target creature.

Festering Mummy

When Festering Mummy dies, you may put a -1/-1 counter on target creature.

Spiked Pit Trap

Flash
{5}, {T}, Sacrifice Spiked Pit Trap: Choose target creature, then roll a d20.
1—9 | Spiked Pit Trap deals 5 damage to that creature.
10—20 | Spiked Pit Trap deals 5 damage to that creature. Create a Treasure token.

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.