msem-instigator

Germinate, then creatures you control that are Saprolings or have counters on them gain indestructible until end of turn. (To germinate, put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

{T}: Add {R} or {G}.
{T}, Sacrifice Sigil of Savagery: Add {R}{G}.

Flash
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{W}{B}: Kirishima's Escort gets +1/+1 and gains first strike until end of turn.

Target creature you control deals damage equal to its power to target creature you don't control. Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Colossal 4—{5}{U}{U}{U} (You may cast this for its colossal cost to have it enter with four +1/+1 counters; or pay {5}{U}{U}{U} as a sorcery: Put four +1/+1 counters on it if it has none.)
Whenever Megalokraken enters or attacks, reveal the top X cards of your library, where X is Megalokraken's power. You may cast a noncreature spell with mana value X or less from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

When Soul-Capturing Lantern enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{1}, {T}: Add one mana of any color.
{6}, {T}, Sacrifice Soul-Capturing Lantern: Exile target nonland permanent. Activate only as a sorcery.

When Automated Blademaster enters, create a colorless Equipment artifact token named Sword with “Equipped creature gets +1/+1” and equip {1} and attach it to Automated Blademaster.

Flying
Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)

Renown 2 (When this creature deals combat damage to a player, if it isn't renowned, put two +1/+1 counters on it and it becomes renowned.)
When Blind Sharpshooter becomes renowned, it deals 2 damage to target creature defending player controls.

Create two 1/1 white Avatar enchantment creature tokens with prowess.
Conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

[+2]: Create a Vial token. (It's an artifact with “1, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
[–3]: Sacrifice another nonland permanent. If you do, destroy target nonland permanent.
[–9]: You get an emblem with “At the beginning of your end step, create Fallen One, a legendary 6/6 black Faerie Angel Avatar creature token with flying.”

Lifelink
When Runic Soulthief enters, target player loses X life and you gain X life, where X is the number of enchantments you control.

Whenever you gain life, put a +1/+1 counter on Faithful Acolyte.
Faithful Acolyte has lifelink as long as it has four or more +1/+1 counters on it.

When Vitality Maestro enters, you gain 5 life.
Recite {G}{W} (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.)

Haste
Other Elementals you control get +1/+0 and have haste.

Whenever a creature you control dies, each opponent discards a card.
Revive {6}{B} ({6}{B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Frenzy 1 (Whenever this creature attacks and isn't blocked, it gets +1/+0 until end of turn.)
Whenever Trading Traitor deals combat damage to a player, you lose life equal to the number of unblocked attacking creatures you control and draw that many cards.

Enchant creature
Enchanted creature gets +2/+0.
When Malignance is put into a graveyard from the battlefield, return Malignance to its owner's hand.
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

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.)

Trample
When Varagan Packmaster enters, create a Treasure token, then exile the top card of your library. Until the end of your next turn, you may play that card.

Deathtouch
Menagerie — When Sting-Hopper enters, if there are five or more creature types among creatures you control, target player reveals their hand. You choose a creature card from it. That player discards that card.

Snowy Misthorn can block creatures with distorted as though it was tapped.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{6}: Unlock Ancient Maze. If the revealed card is green, put it into your hand. Otherwise, put it on top of your library.

Whenever IG-2 Disassembler enters or attacks, you may sacrifice an artifact. When you do, IG-2 Disassembler deals 2 damage to target player or planeswalker.