Hapatra, Vizier of Poisons

Whenever Hapatra, Vizier of Poisons deals combat damage to a player, you may put a -1/-1 counter on target creature.
Whenever you put one or more -1/-1 counters on a creature, create a 1/1 green Snake creature token with deathtouch.

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Diabolic Intent

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a card, put that card into your hand, then shuffle.

Seshiro the Anointed

Other Snake creatures you control get +2/+2.
Whenever a Snake you control deals combat damage to a player, you may draw a card.

Village Rites

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Generous Patron

When Generous Patron enters the battlefield, support 2. (Put a +1/+1 counter on each of up to two other target creatures.)
Whenever you put one or more counters on a creature you don't control, draw a card.

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

Despair

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Until end of turn, creatures you control gain menace and "Whenever this creature deals combat damage to a player, that player discards a card."

Driven

Until end of turn, creatures you control gain trample and "Whenever this creature deals combat damage to a player, draw a card."

Driven // Despair

Stinging Shot

Put three -1/-1 counters on target creature with flying.
Cycling {2} ({2}, Discard this card: Draw a card.)

Splendid Agony

Distribute two -1/-1 counters among one or two target creatures.

Forest

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Virulent Wound

Put a -1/-1 counter on target creature. When that creature dies this turn, its controller gets a poison counter.

Obelisk Spider

Reach
Whenever Obelisk Spider deals combat damage to a creature, put a -1/-1 counter on that creature.
Whenever you put one or more -1/-1 counters on a creature, each opponent loses 1 life and you gain 1 life.

Devoted Druid

{T}: Add {G}.
Put a -1/-1 counter on Devoted Druid: Untap Devoted Druid.

Blowfly Infestation

Whenever a creature dies, if it had a -1/-1 counter on it, put a -1/-1 counter on target creature.

Chatterfang, Squirrel General

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
If one or more tokens would be created under your control, those tokens plus that many 1/1 green Squirrel creature tokens are created instead.
{B}, Sacrifice X Squirrels: Target creature gets +X/-X until end of turn.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Ammit Eternal

Afflict 3 (Whenever this creature becomes blocked, defending player loses 3 life.)
Whenever an opponent casts a spell, put a -1/-1 counter on Ammit Eternal.
Whenever Ammit Eternal deals combat damage to a player, remove all -1/-1 counters from it.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Swamp

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Cinderhaze Wretch

{T}: Target player discards a card. Activate only during your turn.
Put a -1/-1 counter on Cinderhaze Wretch: Untap Cinderhaze Wretch.

Ivy Lane Denizen

Whenever another green creature enters the battlefield under your control, put a +1/+1 counter on target creature.

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

Festering Mummy

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

Corrupted Conviction

Flourishing Defenses

Whenever a -1/-1 counter is put on a creature, you may create a 1/1 green Elf Warrior creature token.

Nest of Scarabs

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

Fynn, the Fangbearer

Deathtouch
Whenever a creature you control with deathtouch deals combat damage to a player, that player gets two poison counters. (A player with ten or more poison counters loses the game.)

Hapatra's Mark

Target creature you control gains hexproof until end of turn. Remove all -1/-1 counters from it. (A creature with hexproof can't be the target of spells or abilities your opponents control.)

Luxior, Giada's Gift

Equipped creature gets +1/+1 for each counter on it.
Equipped permanent isn't a planeswalker and is a creature in addition to its other types. (Loyalty abilities can still be activated.)
Equip planeswalker {1}
Equip {3}

Search for Blex

Look at the top five cards of your library. You may put any number of them into your hand and the rest into your graveyard. You lose 3 life for each card you put into your hand this way.

Blex, Vexing Pest

Other Pests, Bats, Insects, Snakes, and Spiders you control get +1/+1.
When Blex, Vexing Pest dies, you gain 4 life.

Blex, Vexing Pest // Search for Blex

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Banewhip Punisher

When Banewhip Punisher enters the battlefield, you may put a -1/-1 counter on target creature.
{B}, Sacrifice Banewhip Punisher: Destroy target creature that has a -1/-1 counter on it.