msem-instigator

Haste
Whenever Tortle Waymaker becomes blocked, it explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Trial 4 (As you cast this spell, an opponent of your choice may pay 4 life. If they don't, they fail the trial.)
When Treacherous Devil enters, if an opponent passed the trial, that player gains control of Treacherous Devil.

Whenever Twitchy Pyromancer enters or attacks, it deals 1 damage to any target. Whenever a creature dealt damage this way dies this turn, upgrade Twitchy Pyromancer. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• Menace
• Prowess

Menace
Whenever a player gains life, that player sacrifices a permanent.

Haste
When Wretched Merfolk enters, target creature can't block this turn.

When Yamisaran Bladedancer enters, you may attach an Equipment you control to target creature you control.

Young Dragonheart gets +1/+0 and has first strike as long as you control a legendary creature.

Other Rebel creatures you control get +1/+0.
When Youthful Renegade enters, create a 1/1 white Rebel creature token.

Whenever Zana, the Dreamer attacks, you may pay {3}{R}{R}. If you do, for each attacking nontoken creature you control, create a tapped and attacking token that's a copy of it, except the tokens aren't legendary. Exile those tokens at the beginning of the end step.

Whenever two or more creatures an opponent controls block, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Enchanted creatures you control have menace.

Whenever Zealous Scaleblight becomes tapped, it deals 1 damage to any target.

{G}: Tap Adaptive Troll. It gains indestructible until end of turn.
At the beginning of each upkeep, if Adaptive Troll was dealt lethal damage last turn, put a counter of your choice on it from among vigilance, deathtouch, reach, trample, and +1/+1.

{T}: Adept Fisherman voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Adept Fisherman phases in, you gain 2 life.

Trample
Wanderlust — Whenever Akkrixian Assailants attacks, if you control four or more differently named lands, put a +1/+1 counter on it.

Alluring Rider must be blocked if able.
Attain {4}{G} ({4}{G}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Trample
As long as it's an opponent's turn, Ambushing Alligator is a blue Bird with base power and toughness 1/1 and has flying and hexproof.

Whenever another nontoken creature you control enters, create a 1/1 green Saproling creature token.
{1}{G}, {T}: Populate. (Create a token that's a copy of a creature token you control.)

Trample
When Ashka Ritualist enters or whenever you cast a spell, if {R}{W} was spent to cast it, create two 1/1 red and green Warrior creature tokens. Put a +1/+1 counter on Ashka Ritualist.

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 blocked by creatures with power 1 or less.

Ward—Exile three cards from your graveyard. (Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player exiles three cards from their graveyard.)
Menagerie — Astralhorn Familiar gets +2/+2 as long as there are five or more creature types among creatures you control.

Flash
When Blade of Mautakesh enters, creatures you control gain poisonous 1 until end of turn. (Whenever those creatures deal combat damage to a player, that player gets a poison counter. Multiple instances of poisonous trigger separately.)

Branch Prowler can't be blocked except by creatures with flying.

Trample
Whenever Charging Cassowary deals combat damage to a player, you may cast a copy of an Adventure of a permanent you control.

Concord — When Coralight Communer enters, if there are four or more card types among permanents you control, draw a card.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Crusher Beetle can't be blocked by more than one creature.