msem-instigator

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you scry or search your library, add a quest counter.
1 — Target creature you don't control gets -3/-0 until your next turn.
2 — Reveal cards from the top of your library until you reveal a nonland card, then put the revealed cards into your hand.
3 — Reveal the top card of your library. If its mana value is less than or equal to the number of cards in your hand, you may cast it without paying its mana cost.

Infiltrate (Whenever one or more attacking creatures you control aren't blocked, this creature gets +1/+1 until end of turn.)
When Exile's Vanguard enters, tap target creature. That creature doesn't untap during its controller's next untap step.

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 Covert Reinforcement enters, exile target nonland permanent an opponent controls until Covert Reinforcement leaves the battlefield.

Menace
When Lone Zombie and at least two other creatures attack, transform Lone Zombie.

Until end of turn, you may play cards you don't own from exile. Scry 1.

Deathtouch
When a creature you control scavenges Kinsang Duskblade, put a deathtouch counter on that creature.
Scavenge {2}{B} ({2}{B}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

When Vivid Hallucination blocks or becomes blocked, return it to its owner's hand.

When Candlecrown Stag enters, choose one or both —
• Exile target card from a graveyard.
• You gain 3 life.

Return target creature to its owner's hand.
Kindle 1—{U} ({U}, Exile this card from your graveyard: Create a 1/1 colorless Elemental creature token. Kindle only as a sorcery.)

Reach
Prismatic — Whenever you cast a multicolored spell, you gain 2 life.

Return target creature card with mana value 3 or less from your graveyard to the battlefield. If its mana value is less than 3, you gain life equal to the difference.

Children of the Void has hexproof as long as it's your turn.
Children of the Void can't attack or block unless you reappropriate (exile exactly two cards from your hand and/or graveyard).

Desert Slaughterer can't block.
{B}, Remove a +1/+1 counter from a creature you control: Return Desert Slaughterer from your graveyard to the battlefield with a +1/+1 counter on it.

When Sewer Dweller enters or dies, create a 1/1 black Rat creature token with “This creature can't block.”

Target player sacrifices a creature.
Create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

Indestructible
As long as your devotion to black is less than five, Erebos isn't a creature.
Other creatures you control dying causes abilities of that creature to trigger as though it entered.
{2}{B}: Each opponent loses 1 life. You gain life equal to the life lost this way.

Any number of target creatures you control each have base power and toughness 3/3 and become Beasts in addition to their other types until end of turn.
Reconstruct {2}{G}{G} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

When Fatetwist Shaman dies, reveal the bottom card of your library. You may put it on top of your library.

When Gilded Yak enters, you gain 3 life.

Whenever Almgrove Spellblade attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Exile the top two cards of your library. Until end of turn, you may play cards exiled by Almgrove Spellblade.

Colossal 3—{6}{R} (You may cast this for its colossal cost to have it enter with three +1/+1 counters; or pay {6}{R} as a sorcery: Put three +1/+1 counters on it if it has none.)

Return target creature card from your graveyard to the battlefield. If you control a Demon, each opponent loses 3 life.

Until end of turn, all creatures gain deathtouch and “When this creature dies, its controller loses 2 life.”

As Reflective Stalker enters, choose a noncreature card name.
When Reflective Stalker enters, if it was cast, create a token that's a copy of it.
Spells your opponents cast with the chosen name cost {2} more to cast.