msem-instigator

Whenever The Pursuit of Science enters or a nontoken creature you control dies, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
Clues you control have “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”

At the beginning of your end step, create a 1/1 colorless Human creature. Put a sacrifice counter on it.
Creature tokens you control with sacrifice counters on them can't attack or block and have “Sacrifice this creature: Add {C}.”

As Theodore Harper, Head Librarian enters, choose Fact or Fiction.
• Fact — Permanent spells you cast cost {1} less to cast. This effect can't reduce the amount of mana a spell costs to cast to less than one mana.
• Fiction — When Theodore Harper enters, return a permanent card from your graveyard to your hand.

Thicketed Path enters tapped unless you control one or fewer other lands.
{T}: Add {G} or {W}.
Cycling {2} ({2}, Discard this card: Draw a card.)

At the beginning of each player's draw step, that player draws two additional cards. At the beginning of their next end step, they discard their hand.

At the beginning of combat on your turn, tap Tinchor, put two +1/+1 counters on him, you draw a card, and you lose 1 life.
When Tinchor dies, put his counters on target Human you control.

Whenever a nontoken creature dies, you may exile that card. If you do, return each other card exiled with Tome of the Lidless Gaze to its owner's graveyard.
At the beginning of your upkeep, if you control no Eyes, create a token that's a copy of a card exiled with Tome of the Lidless Gaze except it's a 2/2 Eye Horror with flying in addition to its other types.

Torrid Path enters tapped unless you control one or fewer other lands.
{T}: Add {R} or {W}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Tracking Party enters with a +1/+1 counter on it.
{T}, Remove a +1/+1 counter from Tracking Party and exert it: Destroy target artifact or enchantment. (An exerted creature won't untap during your next untap step.)

When Transformative Paints enters, create a 1/1 white Human creature token, then attach Transformative Paints to it.
Equipped creature gets +1/+0 and has prowess.
Equip {3}

Kicker—Sacrifice a creature. (You may sacrifice a creature in addition to any other costs as you cast this spell.)
You draw two cards and you lose 2 life. If this spell was kicked, you draw four cards and you lose 4 life instead.

When Trepid Deserters enters, target creature you control gets +2/+0 until end of turn.

When Tumultuous Shrine enters or is put into a graveyard from the battlefield, up to one target land you control becomes a 4/4 Elemental creature with haste. It's still a land.

Until end of turn, target creature loses all abilities and has base power and toughness 1/1. If it's attacking, counter all triggered abilities from that source.

Flash
When Turned by Fear enters, return up to one target creature to its owner's hand.
At the beginning of combat on your turn, up to one target creature gains menace until end of turn.

Flying
{1}{R}{R}{R}: Return Umbral Hunter from your graveyard to your hand. If it's the declare attackers step, up to one target attacking creature gets +3/+1 until end of turn.

Search your library for up to four basic land cards, reveal them, put them into your hand, then shuffle. You may play an additional land this turn.

Whenever one or more creatures you control deal combat damage to a player, that player discards a card. Then that player may discard another card. If they don't, create two 2/1 black Nightmare creature tokens with “This creature can't block.”
Fleeting {1}{B}{B} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

At the beginning of your upkeep, you may create a Treasure token. If you do, an opponent of your choice creates a tapped Treasure token.

When Unwitting Fanatic enters, create a 3/2 colorless Horror creature token.
Sacrifice Unwitting Fanatic: Another target permanent you control gains hexproof and indestructible until end of turn.

Enchant creature
When Valorous Ideal enters, target creature can't block this turn.
Enchanted creature gets +2/+0 and attacks each combat if able.
When Valorous Ideal is put into a graveyard from the battlefield, return Valorous Ideal to its owner's hand.

Once each turn, when Vedu, the Deepdrinker enters or you attack with one or more Horrors, you may tap up to two target permanents. If Vedu isn't a token, put two stun counters on each of those permanents.
{2}{U}{U}, Discard Vedu: Create a token that's a copy of Vedu, the Deepdrinker, except it's 4/4 and isn't legendary. Activate only as a sorcery.

Flying
Whenever Venerated Sanctity deals combat damage to a player, put a faith counter on it. Then you may pay {X}{W} and sacrifice Venerated Sanctity. When you do, exile target nonland permanent with mana value less than or equal to X plus the number of faith counters on Venerated Sanctity.

Whenever you attack, create an X/X red Elemental creature token that's tapped and attacking, where X is the number of attacking creatures.
Fleeting {1}{R} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

When Vile Progenitor enters, create a 3/2 colorless Horror creature token.
As long as you control five or more lands, Horrors you control get +1/+1 and have trample.
Evoke {1}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)