msem-instigator

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
At the beginning of your upkeep, create a token that's a copy of the enspirited card. It gains haste until end of turn. Exile it at the beginning of the next end step.

{2}{R}: Thespian Soldier gains first strike until end of turn.

When Theurgist of the Depths enters, for each card type, you may exile a card of that type from your graveyard. Target opponent separates those cards into two piles. Put all cards from the pile of your choice into your hand.
Recite {B}{G}{U} (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.)

Whenever a creature enters under an opponent's control, draw a card unless that player pays {1}.

When Thoughtgrinder enters, each player discards a card.
Unearth {1}{U}{B} ({1}{U}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

Flash
When this creature enters, you may return target instant or sorcery card in a graveyard or nonland permanent to its owner's hand.
Whenever this creature attacks, you may cast a spell from your hand with mana value less than this creature's power without paying its mana cost.

Menace (This creature can't be blocked except by two or more creatures.)

When Threshing Sundew enters, merge up to one target creature card in your graveyard under it. Threshing Sundew has that card's abilities.
When Threshing Sundew dies, return all other cards merged with it to their owner's hand.

Whenever Thrinax Sporemother or another nontoken creature you control dies, create a 1/1 green Saproling creature token.
Whenever a creature card is exiled from your graveyard, create a 1/1 green Saproling creature token.

Flying
When Thunder Shrike enters, choose up to two target permanents. For each of those permanents, you may tap or untap it.

Vanguard — Whenever a creature you control attacks alone, it gets +1/+1 and gains menace until end of turn.

Flash
Cycling {2} ({2}, Discard this card: Draw a card.)

Whenever Tide Crasher attacks, if you control another Merfolk, tap target creature defending player controls.

Whenever you cast your first noncreature spell each turn, you may draw a card. If you do, discard a card.

When Timecrafter Lafterii enters, choose target permanent with one or more time counters on it, then put two time counters on it or remove two time counters from it.

Double strike (This creature deals both first-strike and regular combat damage.)
If three or more creatures are attacking you, you may cast Timely Commander as though it had flash.

Flying

Advance {3}{B}{B} (Cast this for {3}{B}{B} to advance it as it enters. {3}{B}{B}: Advance this as a sorcery.)
Whenever Tireless Archivist advances, search your library for a card, put it into your hand, then shuffle.

Flying
Tribute 2 (As this creature enters, an opponent of your choice may put two +1/+1 counters on it.)
When Tireless Vulture enters, if tribute wasn't paid, each opponent loses 3 life. You gain life equal to the life lost this way.

Colossal 2—{6}{U} (You may cast this for its colossal cost to have it enter with two +1/+1 counters; or pay {6}{U} as a sorcery: Put two +1/+1 counters on it if it has none.)
When Titanic Fathomclaw's colossal ability puts one or more counters on it, return target instant or sorcery card from your graveyard to your hand.

When Tomb-Raider Duo enters, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
Satrapycycling {2} ({2}, Discard this card: Search your library for a Satrapy card, reveal it, put it into your hand, then shuffle.)

You may put cards with mana value 2 or less that permanents you control explore into your hand as though they were lands. (You won't get the counter if you do.)
Whenever Torch of Those Underfoot attacks, it explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Flying
When Tormentor Harpy enters, if there are three or more creature cards in your graveyard, target creature an opponent controls gets -3/-3 until end of turn.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)