msem-instigator

Whenever Gallant Chevalier attacks or blocks, put a +1/+1 counter on it and each other creature you control with a +1/+1 counter on it.

Enchant creature
Enchanted creature gets +4/+4 and has trample.
When enchanted creature dies, create a 4/4 green Beast creature token with trample.

Menace
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{R}: Another target creature you control gains menace until end of turn.

When Cognitive Fumigator enters, target opponent reveals their hand. You may choose a nonland card from it and exile that card. If you do, that player draws a card.
Recite {2}{U} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

Enchant creature
Enchanted creature gets -2/-0.
{3}{U}{U}: Submerge enchanted creature. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

When this creature enters, create a Weapon token, then attach it to a creature you control. (It's an Equipment artifact token with equip {2} and “Equipped creature gets +1/+1”.)
Arise {5}{R} ({5}{R}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

Clockwork Gaucho enters with a +1/+1 counter on it.
Other artifact creatures you control get +1/+1 for each +1/+1 counter on Clockwork Gaucho.
{T}: Put a +1/+1 counter on Clockwork Gaucho.

({T}: Add {U}.)
As Seaside Grotto enters, you may pay 1 life. If you don't, Seaside Grotto enters tapped.
Basic lands you control have “{T}: Add {U}.”

Whenever you cast a spell, Wandering Precursor gets +1/+0 until end of turn for each color of mana spent to cast that spell.

Stampede — Whenever Knotvine Preserver and a creature with greater power attack, until end of turn, attacking creatures you control gain “When this creature dies, return it to its owner's hand.”

When Sadistic Indulgence enters, create three 1/1 white Human creature tokens with “This creature can't attack or block.”
Pay 1 life: Destroy target nonland permanent you control.

At the beginning of combat on your turn, you may pay {2}{R}{R}. If you do, create a 4/4 red Dragon creature token with flying and haste. Exile that token at end of combat.
Ferocious — Whenever Xiusheng of the Dragon Realm attacks, if you control a creature with power 4 or greater, Xiusheng gains double strike until end of turn.

When Fading Memories enters, exile target creature card from a graveyard.

Exile target permanent, then return that card to the battlefield under its owner's control.
Draw a card.

Defender
Whenever Derelict Watcher or another Scarecrow you control enters, create a 1/1 black Bird creature token with flying.

Enchant opponent
When Pathless Shallows enters, exile target creature enchanted player controls until Pathless Shallows leaves the battlefield.
Enchanted player can't cast spells with the same name as the exiled card.

Each creature has haste and “At the beginning of combat on your turn, choose an opponent at random. This creature attacks that player this combat if able.”

Qi-Long Shrine enters tapped.
{T}: Add {U} or {R}.
{U/R}, {T}, Sacrifice Qi-Long Shrine: Put a +1/+1 counter on target creature you control. Activate only as a sorcery.

Reach
Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Colossal 3—{7}{R}{R} (You may cast this for its colossal cost to have it enter with three +1/+1 counters; or pay {7}{R}{R} as a sorcery: Put three +1/+1 counters on it if it has none.)
Flying
Each creature you control with a counter on it has double strike.

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. Create a 1/1 green Elf creature token.

Whenever this enchantment enters or one or more cards leave your graveyard, create a 2/2 black Zombie creature token.
{1}{W}, Discard a card: Tap target nonland permanent and put a stun counter on it. It loses all abilities for as long as it remains tapped.

Defender
Whenever you cast an enchantment, instant, or sorcery spell, scry 1 if it's the first time this ability has resolved this turn. If it's the second time, Prismscale Piranhas can attack this turn as though it didn't have defender. If it's the third time, whenever Prismscale Piranhas deals combat damage to a player this turn, draw a card.

Menace
Sacrifice another artifact: Scrap Buggy becomes an artifact creature until end of turn.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

When Jara Disciplinarian enters, each player sacrifices a creature.