msem-instigator

{B}, {T}, Discard a card: Create a 1/1 black Skeleton creature token.
{B}, {T}, Sacrifice a creature: Put a +1/+1 counter on each Skeleton you control.

When Savannah Huntsman enters, it deals X damage to target creature or planeswalker, where X is the number of counters among permanents you control.

Vigilance
When Kahroba Champion enters, creatures you control get +1/+1 until end of turn.

When Mining Rover Manager enters, create a 1/1 colorless Servo artifact creature token.

Destroy target creature or planeswalker.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

Flying
Sacrifice Nimbus Glider: Creatures you control gain flying until end of turn.

Bloodprice {2}{B}{B} (You may cast this card by sacrificing a creature and paying its bloodprice.)
Return target creature card from your graveyard to your hand. If you cast this spell for its bloodprice, return that card to the battlefield instead.

When Urisk Fiddler enters, draw a card.

Vigilance
Sha'Iv's Emissary gets +1/+1 as long as you control a blue or red permanent.

Create three 1/1 colorless Spirit creature tokens.

Flash (You may cast this spell any time you could cast an instant.)
When Mist Lurker enters, tap all creatures you don't control.

Flying
Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
Your opponents can't cast spells during combat and can't activate abilities during combat unless they're mana abilities.

Abandoned Chamber enters with X story counters on it.
{3}, {T}, Remove all story counters from Abandoned Chamber and exile it: Return a card from your graveyard to your hand for each counter removed this way.

Trample
Harmony — Avalanche Drummer deals 1 damage to any target.
When Avalanche Drummer enters, harmonize. (Trigger up to one harmony of a permanent you control.)

Lifelink
Whenever an opponent loses life, you may pay {2}. If you do, choose one—
• That player discards a card.
• Put a +1/+1 counter on Adversary Ancestor.

Hard Bargain deals 2 damage to target creature or planeswalker an opponent controls and you gain 2 life. Then if you have more life than that opponent, draw a card.

{T}, Pay 1 life: Add {U} or {B}.
{1}, {T}, Sacrifice Unlit Alley: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Trample
{3}, Discard Gilded Ram: Draw a card, gain 2 life, and create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Whenever a permanent you control leaves the battlefield, you may return another card with lesser mana value that shares a type with it from your graveyard to your hand.

Advance {3} (Cast this for {3} to advance it as it enters. {3}: Advance this as a sorcery.)
Whenever Wastes Scrambler advances, put your choice of a +1/+1, first strike, menace, trample, or vigilance counter on it. If {R}{W}{B} was spent to advance it, repeat this process twice.
Crew 1

Descended Countryside enters tapped.
{T}: Add {G} or {W}.
Morph {2} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

When Quandary Seer enters, target player mills three cards. You shuffle up to three cards from your graveyard into your library.

Whenever one or more cards leave your graveyard for the first time each turn, each player loses 1 life and you draw a card.

Creatures you control get +1/+1 and gain trample until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)