msem-instigator

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

Equipped creature gets +1/+0 and has “Whenever this creature deals combat damage to a player, draw a card.”
Equip {3}

First strike
Other Foxes you control get +1/+1.
Whenever a Fox you control becomes blocked, it deals 1 damage to each creature blocking it.

At the beginning of each player's draw step, that player draws two additional cards. At the beginning of their next end step, they discard their hand.

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

Other creatures have haste and attack each combat if able.
Nonland cards in your hand have paranoia {4}. (The owner of a card with paranoia {4} may cast it from their hand for {4} when a permanent they control leaves the battlefield.)

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.

Prismatic — Whenever you cast a multicolored spell, Thorny Bushwacker has base power and toughness 5/3 until end of turn.

Target creature gets +2/+0 and gains haste until end of turn.
Fabled {2}{R} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that creature.)

Target creature gets +1/+1 until end of turn for each creature you control.
Inscribe {3}{R} ({3}{R}: 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.)

Untap target creature and gain control of it until end of turn. That creature gains haste until end of turn.

Equipped creature gets +1/+0 and has menace.
Equip {3}

Menace (This creature can't be blocked except by two or more creatures.)

Attacking creatures get +2/+0 until end of turn.
Armed — Equipped creatures you control get an additional +1/+0 until end of turn.

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.

Vigilance, trample
When Threshold Guardian enters, return a creature you control to its owner's hand.

As an additional cost to cast this spell, discard a card.
Draw two cards.

Thriving Bluff enters tapped.
As Thriving Bluff enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

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.