msem-instigator

{2}{U}{B}: Return Depth Charger to its owner's hand. If you do, return target creature to its owner's hand. That player discards a card.

When Dream Keeper enters, each player conjures a card named Fatigue and puts it on top of their library. (It's a colorless sorcery that costs {2} with “Draw a card.”)
Whenever a player draws a card except the first one they draw in each of their draw steps, each opponent mills a card.

Fahrib's Tongue can't be blocked by creatures with two or more creature types.
Whenever Fahrib's Tongue deals combat damage to a player, that player loses 1 life for each creature that dealt damage to them this turn.

Flying, deathtouch

Shrewd Sikoyo can't be blocked by creatures with power 4 or greater.
Shrewd Sikoyo gets +1/+0 as long as you have at least two more cards in hand than any opponent.

At the beginning of each player's upkeep, that player may sacrifice a creature. If they don't, they discard a card.

Menace
Whenever Margarete or another creature you control dies, up to one target creature you control cackles. (Put a menace counter on it. If it already has menace, it deals 1 damage to each opponent instead.)
Once each turn, when Margarete or another creature you control with menace dies, you may torment each opponent. (They lose 3 life unless they discard a card or sacrifice a nonland permanent.)

When Sahra Poet-Priest enters, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
{R}: Sahra Poet-Priest gets +1/+0 until end of turn.

Flying
When Ascetic of the Folded Fan enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Each creature you control with a +1/+1 counter on it has vigilance.

Vigilance
Unveil {2}{G}{W} ({2}{G}{W}: Transform this. Unveil only as a sorcery.)

{1}, {T}, Move a -1/-1 counter from another creature onto Harried Apothecary: Each opponent loses 1 life and you gain that much life.

Instant and sorcery spells you cast cost {1} less to cast.

{1}{U}{R}, {T}: Create a token that's a copy of another target creature, except it's an artifact in addition to its other types and has “Whenever this creature is dealt damage, destroy it.”

When Lustrebloom Diviner enters, create a Treasure token.
At the beginning of each end step, if you spent three or more colors of mana to cast spells this turn, you gain 3 life. If you spent {W}{U}{B}{R}{G}, draw a card.

When Sarrutu Worldbinder enters, create two 1/1 red Elemental creature tokens.
{1}{U}, {T}: Elementals you control gain flying until end of turn.
{2}{R}, {T}: Elementals you control get +2/+0 until end of turn.

Menace
Stalker of Myth gets +1/+0 for each creature you control with chronicle.
{2}, Remove a counter from a permanent you control: Draw a card, then discard a card.

Prowess
Whenever Steamwalker attacks, you may discard a card. If you do, draw a card, then catalyze. (The next spell you cast this turn costs {1} less to cast.)

Flying, haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Prowess
Whenever you cast a noncreature spell, audition for blue or for red. (Create a 1/1 Construct Actor creature token, a Wizard Role giving 2/2 and prowess, a Warlock Role giving 2/1 and flying, or a Warrior Role giving 3/2 and trample. Roles replace older ones.)

{1}, {T}, Pay 1 life: Put a +1/+1 counter on target creature you control.
{T}, Remove a counter from a permanent you control: Draw a card.

Flying, deathtouch
When Bloodsucking Pihuchen enters, choose a nonland card name.
Whenever a permanent with the chosen name enters, each opponent loses 1 life and you gain 1 life.

{B}{G}, {T}: Reveal the bottom card of your library and exile it. Target creature gets +X/-X until end of turn, where X is that card's mana value.

Deathtouch
{B}{G}, Exile Frosted Adder from your graveyard: Return another target creature card from your graveyard to your hand.

Whenever another nontoken creature you control dies, create a 1/1 green Saproling creature token.
{B}{G}, {T}, Sacrifice a creature: Return target permanent card from your graveyard to your hand.

Deathtouch
Unveil {3}{B}{G} ({3}{B}{G}: Transform this. Unveil only as a sorcery.)