msem-instigator

When Conjured Shade dies, target creature you don't control gets -1/-1 until end of turn.

Haste
When Magma Crawler enters, creatures you control with flash or haste get +1/+1 until end of turn.

Flying
When Tormentor Harpy enters, if there are three or more creature cards in your graveyard, target creature an opponent controls gets -3/-3 until end of turn.

Deathtouch
Chronicle (As this enters and after your draw step, add a lore counter. Stop after III.)
[Lore I-II] You may sacrifice another creature. If you do, draw a card.
[Lore III] Remove all lore counters from Astral Leech. Each opponent sacrifices a creature.

When Trident of Benediction enters, create two 1/1 white Merfolk creature tokens.
Equipped creature has vigilance and “Whenever this creature attacks or blocks, creatures you control get +1/+1 until end of turn.”
Equip {2}

Renown 2 (When this creature deals combat damage to a player, if it isn't renowned, put two +1/+1 counters on it and it becomes renowned.)
Each creature you control with a +1/+1 counter on it has indestructible.

At the beginning of your upkeep, choose an opponent. That player creates a 3/2 colorless Horror creature token.
{2}: Target opponent gains control of Deepdrinker's Effigy.

When Sandmouth Dragon enters, another target creature you control gets +3/+0 until end of turn.
Mirage {2}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Noncreature spells you cast cost {1} more to cast.
Noncreature spells your opponents cast cost {1} more to cast unless that player controls more creatures than you.

When Babyscale Bruiser enters, you may reveal a creature card from your hand. If you do, Babyscale Bruiser deals damage to target creature an opponent controls equal to the revealed card's power. That creature deals damage equal to its power to Babyscale Bruiser.

Choose one —
• Kilnfire deals 1 damage to each creature and planeswalker target player controls.
• Destroy target artifact.

Whenever a creature you control enters, if its mana value is greater than the number of bloom counters on From a Seed, put a bloom counter on From a Seed.
Creatures you control get +1/+1 for each bloom counter on From a Seed.

{T}: Add {C}.
{T}, Reappropriate: Add {R} or {G}. (Exile exactly two cards from your hand and/or graveyard.)

When Ontarachie Envoy enters, nourish, then germinate. (To nourish, put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token. To germinate, put a +1/+1 counter on a creature you control or create a 1/1 green Saproling creature token.)

Vigilance
{T}: Target instant or sorcery card in your graveyard with mana value 3 or less gains flashback {0} until end of turn. Activate only as a sorcery. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Destroy target creature or planeswalker.

When Bjarndyr Mender enters, other creatures you control get +1/+1 and gain indestructible until end of turn.

Flying

Flying, lifelink, haste
{W}{U}{B}{R}{G}, Exile Remi Amber, Slyten Specialist: Return Remi Amber to the battlefield transformed at the beginning of your next main phase.

Synchronous Battle Armor and equipped creature get +1/+1 for each artifact you control.
Whenever equipped creature attacks, tap up to three target creatures.
Reconfigure {3}{U}{U} ({3}{U}{U}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Search your library for a card and put it into your hand, then shuffle. You lose life equal to the number of cards in your hand.

Whenever you cast a black spell, put a +1/+1 counter on Flenser's Lieutenant.
{B}{B}: Return Flenser's Lieutenant from your graveyard to your hand.

Jungle Shrine enters tapped.
{T}: Add {R}, {G}, or {W}.

Whenever Uncanny Allocator enters or attacks, give any number of permanents and/or players with counters on them another counter of each kind already there.

Archive 6 (As this enters, shuffle the top six cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever one or more Dragons you control attack, you may cast the top card of the archived library without paying its mana cost.