msem-instigator

Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)
When Tutorial Boss enters the battlefield, create a 1/1 blue Pirate creature token.

When Twilight Vigil enters the battlefield, scry 2, then put a night counter on it.
Death knell — Put a night counter on Twilight Vigil. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
Sacrifice Twilight Vigil: For each night counter on it, you gain 1 life and trigger up to one death knell of a permanent you control.

When Twilight of the Intisuyu enters the battlefield, draw a card, then choose a card name.
Permanents you control with the chosen name have lifelink and ward {1}.

When Twinforged Golem enters the battlefield, create a 3/3 colorless Golem artifact creature token.

Enchant creature
When Twinklewings enters the battlefield, draw a card.
Enchanted creature has flying.

Harmony — Creatures you control gain double strike until end of turn.
When Twirling Duet enters the battlefield, harmonize. (Trigger up to one harmony of one permanent you control.)

Flash
When Twisted Speaker enters the battlefield, return target spell to its owner's hand. That spell's controller loses 2 life.

This spell costs {1} less to cast for each foretold card you own in exile, each permanent you control with foretell, and each card with foretell in your graveyard.
Flying
When Tyrant of Prophecies enters the battlefield, it deals 3 damage to any target.

Flying
When Tyrant of Tributes enters the battlefield, target opponent sacrifices X permanents, where X is half the number of permanents they control, rounded up. You gain X life.

Trample, haste
When Tyrants of Bundan enters the battlefield, tap all lands target player controls. They don't untap during their controller's next untap step.

Flying, vigilance
When Tyriel, Angelic Artisan enters the battlefield, you may search your library for an Equipment card, reveal it, put it into your hand, then shuffle.
Whenever Tyriel attacks, you may put an Equipment card from your hand onto the battlefield, then attach it to Tyriel.

Flash
When Tyrus, Giver to All enters the battlefield and at the beginning of combat on your turn, for each counter on permanents you control, you may move that counter from that permanent to another permanent you control.

When Ulek Elder enters the battlefield, look at the top card of your library. You may put it into your graveyard.

When Unbound Expanse enters the battlefield, if an opponent controls more lands than you, create a Plains token. (It's a basic land with “{T}: Add {W}.”)
{1}{W}, Sacrifice Unbound Expanse: Exile each nonland permanent you control, then return those cards to the battlefield under your control.

When Unburdening Priest enters the battlefield, you may exile any number of creatures you control not named Unburdening Priest, then return those cards to the battlefield under your control.

Hexproof
When Uncharted Leviathan enters the battlefield, target creature can't be blocked this turn.

When Uncovered Idol enters the battlefield, scry 1.
{1}, Sacrifice Uncovered Idol: Put a +1/+1 counter on target creature. Activate only as a sorcery.

When Uncovered Mine enters the battlefield and at the beginning of your upkeep, return a random card from your graveyard to your hand.

When Uncovered Secrets enters the battlefield, search your library for an artifact card, reveal that card, then shuffle and put that card on top.
Concord — Creatures you control get +1/+1 as long as there are four or more card types among permanents you control.

When Undead Archivist enters the battlefield, return target instant or sorcery card from your graveyard to your hand.
Revive {5}{U} ({5}{U}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

When Undead Banneret enters the battlefield, if you control a legendary creature, each opponent loses 4 life.

This spell costs {1} less to cast for each Zombie creature card in your graveyard.
When Undead Harbinger enters the battlefield, return target Zombie card from your graveyard to your hand.

This spell costs {1} less to cast for each artifact you control. (This applies before Treasures are sacrificed for mana.)
When Underhanded Deal enters the battlefield, draw three cards.
Whenever you cast a spell, you lose 1 life.

When Undermarket Favors enters the battlefield, target player discards a card, then mills four cards.
{1}, Sacrifice Undermarket Favors: Draw a card.

Bleed {1}{B} (You may cast this spell for its bleed cost if an opponent lost life this turn.)
When Undermurk Scavenger enters the battlefield, you draw a card and you lose 1 life.