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.

Wu Xing (Add effects based on the number of colors of mana spent to cast this spell.)
1 | Attacking creatures get -3/-0 until end of turn.
3 | Thundering Wrath deals 1 damage to each of those creatures.

Flying
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{R}{R}, {T}: Exile an instant card with mana value 3 or less from your graveyard, then cast a copy of a card exiled with Thunderlash Mystic without paying its mana cost.

Flash
Whenever Thundermane Fox enters 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.

Vigilance, menace, trample, haste
Whenever you cast a spell, you may consume. If you do, put a +1/+1 counter on Thunderous Avarice. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
Whenever an opponent casts a spell, they may consume. If they don't, put a +1/+1 counter on Thunderous Avarice.

Target creature gains hexproof and trample until end of turn. If Thunderous Charge was cast from exile, that creature gets an additional +4/+4 until end of turn.
Orchestrate {G}{G} (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

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

When Thunderstep Ved enters, it deals 1 damage to any target.

Primal {2}{R}{R} (During your turn, you may cast this spell for {2}{R}{R} instead of playing a land.)
Flying, prowess
At the beginning of your end step, if you didn't cast a spell this turn, sacrifice Thunderstride.

When Thunderwhirl Dancer enters, it gets +X/+X until end of turn, where X is the number of +1/+1 counters among creatures you control. Then it fights up to one target creature.

Creature tokens you control get +1/+1.
Whenever Thyra, Winter's Warden enters or attacks, you may pay {1}{G/W}. If you do, create Bruga, a legendary 2/2 green and white Wolf creature token.

Flying
Tianyuren Skycharter has hexproof as long as you control a storied permanent. (Enchantments and legendary permanents are storied.)

Choose one —
• Draw three cards, then discard a card.
• The owner of target nonland permanent puts it on the top or bottom of their library.

As an additional cost to cast this spell, tap any number of untapped storied permanents you control.
Return X target creatures to their owner's hand, where X is one plus the number of permanents tapped this way.

Flash
Menagerie — When Tidal Trickster enters, if there are five or more creature types among creatures you control, you may search your library for a card named Tidal Trickster, reveal it, put it into your hand, then shuffle.

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

Lionize {1}{U} ({1}{U}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following ability until end of turn. You may cast this card on a later turn from exile.)
Sacrifice this creature: Counter target instant or sorcery spell unless its controller pays {X}, where X is this creature's power.

Permanents you control gain indestructible until end of turn. Untap each creature you control.
Cycling {W} ({W}, Discard this card: Draw a card.)

Embellish {3}{B} (If you cast this spell for {3}{B}, create a 1/1 blue Thopter artifact creature token with flying when it enters.)
Tidehollow Lich can't block.
You may cast Tidehollow Lich from your graveyard as long as you control an artifact creature.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
When Tidepool Turtle has three or more +1/+1 counters on it, remove them all and transform it.

Choose target creature you control and target creature you don't control. Flip a coin. If the coin comes up heads, put one of those creatures on top of its owner's library. Otherwise, put both of them on top of their owners' libraries.

Each opponent sacrifices a creature or planeswalker.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Vanishing 4 (This creature enters with four time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Remove a time counter from Tideshift Elemental: You may tap or untap target creature.