msem-instigator

When 1-ST Thankless Companion enters, draw a card.

Whenever you cast a noncreature spell, put a +1/+1 counter on Abjuration Savant. It gains flying until end of turn.
When Abjuration Savant dies, you gain life equal to its toughness.

Whenever you cast an Adventure spell, put a +1/+1 counter on Adventurer Extraordinaire.

Vigilance
{1}{G}: Ajani's Advocate gets +2/+2 until end of turn. Activate only once each turn.

First strike
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.)
Almgrove Champion can only attack or block alone.

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.)
This creature can't be sacrificed.

Vanguard — Whenever a creature you control attacks alone, it gets +1/+1 until end of turn.

Improve {1} ({1}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
When Bridgehaven's Finest enters, create a 1/1 colorless Human creature token.
Other creatures you control get +1/+1 as long as Bridgehaven's Finest has two or more counters on it.

Spells cost {1} more to cast for each colored mana symbol in their mana cost beyond the first. (For example, a spell with mana cost {W}{W} would cost {1}{W}{W} to cast.)

Flying
When Byte Bug enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Flying
When Cadre Hawk enters, you may search your library and/or graveyard for a card named Cadre Hawk, reveal it, and put it into your hand. If you searched a library this way, shuffle.

Flying
Whenever Capricious Wind's Disciple attacks, another target creature in its pack gains double strike until end of turn. (Two or more creatures you control with equal power are in a pack.)

Whenever another creature or enchantment you control enters, you gain 1 life.
{3}{W}{W}, Pay 5 life: Castigated Sister becomes a 5/5 Angel Horror with flying. (This effect doesn't end at end of turn.)

Whenever you cast a spell, if it isn't your main phase, create a 1/1 white Monk creature token, then creatures you control get +1/+1 until end of turn.

{T}: Target creature loses all abilities until end of turn. Exile Chochin the Silent Moth and that creature.

Whenever another creature you control enters, you gain 1 life.
{4}{W}: Return another target creature you control to its owner's hand.

First strike

Whenever Combat Technician attacks, create a 1/1 colorless Servo artifact creature token that's tapped and attacking. Then Combat Technician gets +1/+1 until end of turn for each artifact you control.

When Coralight Mystic enters, create a white Aura enchantment token named Whale's Spirit attached to target creature. The token has enchant creature and “Enchanted creature has lifelink.”

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Curious Cubs has first strike as long as its attacking.
When Curious Cubs has three or more +1/+1 counters on it, remove them all and transform it.

Identity — When Danuri Warcaller enters, if you control at least two other creatures that share a creature type with it, create a 1/1 white Soldier creature token.

{W}, {T}: Target attacking creature gets +1/+1 until end of turn. This ability costs {W} less to activate if it targets a Soldier.

Double strike

Flying
When Delivery Bird enters, if you control an artifact, put a +1/+1 counter on another creature you control.

Lifelink
Sacrifice Devoted Apothecary: Remove a counter from target permanent.