msem-instigator

Whenever a creature you control enters, Timid Thunderhorn gets +X/+X until end of turn, where X is that creature's power.

This spell has flash as long as you control a Soldier.
When Tinyvale Watchkeep enters, untap target creature.

First strike
Noncreature spells with mana value 4 or greater cost {1} more to cast.

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
When Tomb Steward enters, search your library for a card and put it into your graveyard. Then shuffle.

When Tombstone Looter enters, you may draw a card. If you do, discard a card.
Unearth {1}{U} ({1}{U}: 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.)

{G}, {T}: Add one mana of any color. When a creature enters this turn, if that mana was spent to cast it, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Tortle Traveler enters tapped.
When Tortle Traveler enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Haste
Whenever Tortle Waymaker becomes blocked, 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.)

{1}{W}, Sacrifice Town Elder: Return target artifact or enchantment card from your graveyard to your hand.

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Tracker of Wild Places envisions a creature card, you may untap a permanent you control.

Rapport — Whenever Trae, Serpent's Grasp and at least one other creature you control become tapped, each player draws a card. Then Trae, Serpent's Grasp deals 2 damage to each opponent with four or more cards in hand.

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
{2}{W}{W}, Return an unblocked attacking creature you control to its owner's hand: Create a 4/4 white Angel creature token with flying that's tapped and attacking.

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Trained Warhawk enters, create a 1/1 white Soldier creature token.

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

You may exile a land card from your hand rather than pay this spell's mana cost.

Vigilance
When Traveling Duo enters, create a 1/1 colorless Servo artifact creature token.

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
At the beginning of combat on your turn, if you control three or more creatures, Traveling Scholar gets +1/+0 until end of turn.

Trial 4 (As you cast this spell, an opponent of your choice may pay 4 life. If they don't, they fail the trial.)
When Treacherous Devil enters, if an opponent passed the trial, that player gains control of Treacherous Devil.

Treacherous Oasis enters tapped.
{T}: Add {U} or {B}.
{2}{U}{B}: Until end of turn, Treacherous Oasis becomes a Crocodile creature in addition to its other types. It can't be blocked this turn.
Scavenge {1}{U}{B}

{B}: Treacherous Shade gets +1/+1 until end of turn.
{1}{B}{B}: Treacherous Shade gets +3/+3 until end of turn.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
Whenever a Reflection you control becomes the target of a spell, draw a card.

Untap all other artifacts you control during each other player's untap step.
{T}: Untap another target permanent.

Whenever another nontoken creature you control enters, that creature gains haste until end of turn. Then Tremor Seer deals 1 damage to any target.

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

Rhapsody {4}{U}{U} (Pay {4}{U}{U} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever you cast a noncreature spell, Triumvirate Inductee gets +1/+1 until end of turn. Then if its power is 4 or greater, you may tap or untap target permanent.