msem-instigator

Creatures you control have trample, haste, and hexproof.
{2}{G}{G}: Create a 2/2 white Cat creature token.

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Draw X cards, where X is the greatest power among creatures you control. Then you may put a permanent card with mana value X or less from your hand onto the battlefield.

Creatures you control get +1/+1 and gain trample until end of turn.
Reconstruct {4}{G} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

When The Struggle for Death enters, choose target creature you don't control. Any number of creatures you control fight that creature.
Whenever a creature dies, look at the top card of your library. You may put it into your graveyard.

Deathtouch
When The Terror of Shady Cove enters, target opponent sacrifices an artifact. If they can't, create a 3/3 green Slug creature token with deathtouch. Then repeat this process for an enchantment and a nonbasic land.

As Theodore Harper, Head Librarian enters, choose Fact or Fiction.
• Fact — Permanent spells you cast cost {1} less to cast. This effect can't reduce the amount of mana a spell costs to cast to less than one mana.
• Fiction — When Theodore Harper enters, return a permanent card from your graveyard to your hand.

Target creature gets +1/+3 and gains hexproof until end of turn.

Whenever Thicketkeeper perseveres, add {G}{G}. Until end of turn, you don't lose this mana as steps and phases end. (A creature perseveres when it survives damage.)

Reach
Whenever Thicketwalker attacks, you may tap or untap target land.

Trample
Stampede — Whenever Thoctar Yearling and a creature with greater power attack, put a +1/+1 counter on Thoctar Yearling.

Other untapped creatures have hexproof.
Whenever a creature attacks you, put a +1/+1 counter on a creature you control.

Flash
Thorn-Touch Abomination enters with X +1/+1 counters on it.

{T}: Add {G}. If there are three or more creature cards in your graveyard, add {G}{G} instead.

Reach, deathtouch

Flash
When Thornweald Cavalier enters, target creature gets +1/+1 until end of turn. Put a reach counter on it.

Whenever a creature you control phases in, it gets +2/+2 until end of turn.

When Three Seas Squire enters, target creature or Vehicle gets +2/+1 until end of turn.

Thriving Grove enters tapped.
As Thriving Grove enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

Trample, haste
Thriving Hydra enters with four +1/+1 counters on it.
When Thriving Hydra enters, for each other creature you control, put X +1/+1 counters on that creature, where X is four minus its power.
Whenever Thriving Hydra attacks, double the number of +1/+1 counters on each creature you control.

As an additional cost to cast this spell, sacrifice a land.
Creatures you control get +1/+1 and gain trample until end of turn for each land you control.

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
Hexproof
At the beginning of your upkeep, put a +1/+1 counter on this creature.

Trample
Once each turn, if one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on that creature instead.

You may sacrifice a land. If you do, search your library for a land card, put that card onto the battlefield, then shuffle.
Inscribe {3}{G} ({3}{G}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Thuggish Detective can't be blocked by more than one creature.
When Thuggish Detective becomes renowned, you may destroy target noncreature permanent.

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
Trample