msem-instigator

Pressure {3}{B}{G} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
When Sunken-Eye Angler enters, mill three cards. Then if it was cast for its pressure cost, you may return a creature card from your graveyard to the battlefield.

Whenever Supplanter of Realities attacks, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another kind of a counter already there.)
Sacrifice another permanent: Supplanter of Realities gains indestructible until end of turn. Tap it.

Haste
Heroic — Whenever you cast a spell that targets Akroan Siege Captain, put a +1/+1 counter on each creature you control.

Flying, haste
Angel spells you cast cost {1} less to cast.
Other Angels you control get +1/+1 and have haste.

Other Hounds you control get +1/+1.

Whenever you gain life, Clerics you control get +1/+1 and gain trample until end of turn.

Lifelink
Instant and sorcery spells you control have lifelink.
{2}{R}{W}: Copy target instant or sorcery spell. You may choose new targets for the copy.

Lifelink
At the beginning of each player's end step, that player discards each card in their hand, then draws that many cards. When no cards are discarded this way, Dayang, Aspiring Muse deals 2 damage to each opponent.

Flying, haste
Whenever Epoch Warden attacks, you may aetherize another target attacking creature you control. (To aetherize, create a token that's a copy of it, then exile that token.)

Attacking creatures you control get +1/+0.

Flying
Whenever Flying Scorpion attacks, it gets +1/+0 until end of turn for each creature you control that's not attacking.

If another creature you control would die, exile it instead.
When John Furo, the Unfortunate dies, until your next end step, you may play cards exiled with John Furo.

Other Actors you control get +1/+1.
Whenever a permanent you control transforms, Lantern Tender deals 2 damage to any target and you gain 2 life.

Prowess
When One of Purpose enters, if you cast it, create a Function token with “If you cast this spell from your hand, exile it. You may cast it from exile until the end of your next turn.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Whenever Perfecting Forgemaster enters or attacks, you may sacrifice an artifact. If you do, look at the top six cards of your library. You may reveal an Equipment card from among them. Put it onto the battlefield if its mana value is less than or equal to the sacrificed artifact's mana value. Otherwise, put it into your hand. Then shuffle.

Flash
When Pivot-Fist Meditant enters, choose a creature you control. Whenever that creature is dealt damage this turn, it deals that much damage to any other target.

Harmony — Creatures you control get +1/+0 and gain vigilance until end of turn.
When Plume de Val Singer enters, harmonize. (Trigger up to one harmony of one permanent you control.)

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Double strike
Whenever an opponent casts a noncreature spell, Riko, the Paragon deals 2 damage to that player.
Whenever a creature you control becomes blocked, untap it.

Artifact and enchantment spells you cast cost {1} less to cast.
Whenever Risti Salvager attacks, rediscover an artifact or enchantment card. (Look at the top card of your library. You may reveal it and put it into your hand if it's an artifact or enchantment card. Otherwise, put it back or into your graveyard.)

Whenever Sandbluff Inciter attacks, it deals damage to defending player equal to the number of tapped creatures you control.

Each creature you control that has been dealt damage this turn by a source you controlled has indestructible.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{R}{W}: Creatures you control gain flying and haste until end of turn.

First strike
Each other nontoken creature you control enters with an additional +1/+1 counter on it.

Rhapsody {4}{R}{W} (Pay {4}{R}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Lifelink, haste