msem-instigator

First strike (This creature deals combat damage before creatures without first strike.)

{T}: Target creature with power 2 or less can't be blocked this turn.

When Goblin Twinblades enters, create a 1/1 red Goblin creature token.

Haste
{2}{W}, {T}: Hair-Trigger Marshall deals 2 damage to target blocking creature.

Whenever you cast a spell during an opponent's turn, Haughty Priest deals 1 damage to that player.

Trample
Whenever you cast a noncreature spell, crystallize. If you create a Treasure this way, Heartforge Savant deals 1 damage to you for each Treasure you've created this turn. (Put a +1/+1 counter on a creature you control or create a Treasure.)

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
Whenever this creature attacks, if it's merged with another card or token, it deals 2 damage to target player or planeswalker.

Haste
{1}{R}, {T}: Attacking creatures you control get +1/+0 until end of turn.

Double strike
When a creature you control scavenges Hook-Style Trainee, put a double strike counter on that creature.
Scavenge {4}{R} ({4}{R}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Ifram's Cavalier enters with two additional +1/+1 counters on it if you didn't cast it from your hand.

Haste
Ifram's Emissary gets +1/+1 as long as you control a green or blue permanent.

{R}: Igniting Lavaling gets +1/+0 until end of turn.
{4}{R}, Sacrifice Igniting Lavaling: It deals 3 damage to any target.

When Improvisionist enters, if it was the second spell you cast this turn, exile the top card of your library. You may play that card until the end of your next turn.

Whenever Infiltrator of the Anomalous deals combat damage to a player, add {R}. Until end of turn, you don't lose this mana as steps and phases end.

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)

As long as Jadycian Empath is on the battlefield or in your graveyard, it's a land in addition to its other types.
Sacrifice Jadycian Empath: Add one mana of any color.

Whenever Jak, Daring Vanguard or another legendary creature you control enters, creatures you control get +1/+0 and gain haste until end of turn.

Whenever you cast a noncreature spell, you may pay {R}. If you do, untap Kamito Rageweaver.
{T}: Kamito Rageweaver deals 1 damage to target player.

Once each turn, when you sacrifice a land, you may add one mana of any color. Until end of turn, you don't lose this mana as steps and phases end.

First strike
When a creature you control scavenges Laiyru Huntsman, put a first strike counter on that creature.
Scavenge {2}{R} ({2}{R}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Lantern-Bearer Belle gets +2/+0 and has flying as long as you've sacrificed a permanent this turn.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever Loyal Firestarter attacks, you may cast an instant or sorcery spell from your hand with mana value less than or equal to Loyal Firestarter's power without paying its mana cost.

Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)
{1}{R}, Remove a +1/+1 counter from Lt. Daisy Saxon: She deals 2 damage to target player or planeswalker.

First strike
Whenever Martial Maestro attacks, other attacking creatures you control get +1/+0 until end of turn.

Whenever Masha's Vanguard deals damage to a player, you may put a creature card with mana value X or less from your hand onto the battlefield, where X is the amount of damage dealt this way.