msem-instigator

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever a +1/+1 counter is put on Treecrawler Elemental, you may have it fight target creature. (Each deals damage equal to its power to the other.)

Vigilance, reach
When Treeline Archer enters, mill four cards.
{5}{G}: Transform Treeline Archer. Activate only if it's attacking.

Flash (You may cast this spell any time you could cast an instant.)
Reach (This creature can block creatures with flying.)

Prevent all combat damage creatures with flying would deal this turn. Creatures you control gain reach until end of turn.

Whenever Tremor Elemental enters or you draw a card except during your draw step, Tremor Elemental deals 1 damage to each creature.

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

Whenever Tremor Titan enters or attacks, each player sacrifices a permanent. Then you draw a card for each opponent who sacrificed a land this way.

When Trench Breaker enters, put target creature on top of its owner's library.

When Trenchbottom Mariners enters, you lose 3 life, mill three cards, and create a Treasure token.
Whenever Trenchbottom Mariners attacks, you may cast a permanent card from your graveyard by sacrificing another artifact in addition to paying its costs.

Whenever a land you control enters, put a +1/+1 counter on target creature you control.

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

Whenever you cast a spell from your graveyard, you may return target nonland permanent to its owner's hand.
Sacrifice a Clue: Return Trespasser of the Gallows from your graveyard to your hand.

This spell costs {1} less to cast for each card you've drawn this turn.
Create three 1/1 white Soldier creature tokens.

I — Create a 1/1 red Hound creature token.
II — Create a 4/4 green Rhino Warrior creature token with trample.
III — You may have two target creatures you control fight. If you do and exactly one survives, put four +1/+1 counters on that creature.

Trample
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever Tribal Guard mentors a creature, that creature gains trample until end of turn.

Equipped creature has menace.
Whenever equipped creature attacks, look at the top two cards of your library. Put any number of them into your graveyard and the rest back on top of your library in any order.
Equip {2}

When Trident of Benediction enters, create two 1/1 white Merfolk creature tokens.
Equipped creature has vigilance and “Whenever this creature attacks or blocks, creatures you control get +1/+1 until end of turn.”
Equip {2}

{4}{G}{G}, Exile six other cards from your graveyard: Return Trifold Atrocity from your graveyard to the battlefield with three +1/+1 counters on it. Activate only as a sorcery.

Erratic, erratic, erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order. Repeat this process twice.)

{G}, {T}: Target creature with power 4 or greater fights any number of target creatures you control.

Whenever an opponent casts their first spell each turn, that player may pay {1}. If they don't, you may create a Treasure token and you may draw a card.

Copy target spell twice. You may choose new targets for the copies. (A copy of a permanent spell enters as a token.)

Pressure {1}{G}{G} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Trample
Whenever Triplicate Monstrosity deals combat damage to a player, draw a card.

Triplicate Terror can't be blocked unless defending player pays {3}. (They pay it once each combat.)

Creatures you control gain double strike until end of turn. Whenever a creature you control deals combat damage this turn, put a +1/+1 counter on it.