msem-instigator

Whenever Thundering Towershell attacks, return a creature card with mana value 5 or less from a graveyard to the battlefield under your control. Trigger a death knell of that creature.

Flash
Whenever Thundermane Fox enters the battlefield or attacks, target creature you control gains double strike until end of turn.

Thunderous Applause deals damage to any target equal to the number of tapped creatures you control.

Primal {2}{R}{R}
Flying, prowess
At the beginning of your end step, if you didn't cast a spell this turn, sacrifice Thunderstride.

Experience
When Tidepool Turtle has three or more +1/+1 counters on it, remove them all and transform it.

Once each turn, when a creature you control becomes tapped, you may untap that creature and tap up to one target creature.

Take an extra turn after this one. Exile Time if it wasn't fused.
Fuse

Choose target permanent. Take an extra turn after this one. During that turn's untap step, permanents other than the chosen permanent phase out until end of turn. Exile Time Stands Still.

Destroy target non-Xirix permanent. If that permanent had mana value 6 or greater, take an extra turn after this one.

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

When Tinker Tantrum enters the battlefield and at the beginning of your upkeep, you may sacrifice an artifact. If you do, reveal cards from the top of your library until you reveal an artifact card with mana value X or less, where X is 1 plus the sacrificed artifact's mana value. Put that card onto the battlefield and the rest on the bottom of your library in a random order.

Advance {3}{B}{B}
Whenever Tireless Archivist advances, search your library for a card, put it into your hand, then shuffle.

Search your library for an artifact card with mana value X, where X is 1 plus the greatest mana value among artifacts you control, reveal it, put it into your hand, then shuffle.
You may cast Tireless Endeavor from your graveyard by sacrificing an artifact in addition to paying its other costs.

Vigilance
Permanent spells you cast cost {1} less to cast for each 1 damage Tireless Explorer has dealt to players this turn.

{3}, Sacrifice Titanic Fossil: Mill three cards, then you may cast another card with mana value 3 or less from your graveyard without paying its mana cost. Activate only as a sorcery.
{3}{U}{B}: Return Titanic Fossil from your graveyard to the battlefield transformed. Activate only during your turn.

You may tap or untap target nonland permanent.
Catalyze.

At the beginning of each end step, put a +1/+1 counter on equipped creature for each creature that died this turn.
Equip {1}

{X}{X}{W}, {T}, Sacrifice Tome of Loss: Return each creature card with mana value X or less from your graveyard to the battlefield.

Primal {5}{U}{R}
Each player discards their hand, then draws seven cards. If this spell was cast for its primal cost, draw cards equal to the number of cards your opponents discarded this way.

You may put cards with mana value 2 or less that permanents you control explore into your hand as though they were lands.
Whenever Torch of Those Underfoot attacks, it explores.

Winnow
Sacrifice Tormented Echo: Target creature gains winnow until end of turn.

Vigilance
When Tortle Guard enters the battlefield, it explores.

Trample
{4}{R}{R}: Tortle Tinkerer explores. This ability costs {1} less to activate for each artifact you control.

{G}, {T}: Add one mana of any color. When a creature enters the battlefield this turn, if that mana was spent to cast it, it explores.

Tortle Traveler enters the battlefield tapped.
When Tortle Traveler enters the battlefield, it explores.