msem-instigator

Draw three cards. Then discard two cards unless you discard an instant or sorcery card.

Draw three cards, then discard two cards unless you discard a multicolored card.

{1}{B}: Target Knight or Soldier you control gains deathtouch until end of turn.

Rhapsody {4}{U}{U} (Pay {4}{U}{U} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever you draw a card, any number of target players mill two cards.
Whenever This Is Not Our Fate deals combat damage to a player, for each player, you may cast an instant or sorcery card from that player's graveyard without paying its mana cost.

Primal {5}{R}{W} (During your turn, you may cast this spell for {5}{R}{W} instead of playing a land.)
Until end of turn, permanents you control gain indestructible and permanents you don't control lose indestructible. Then if if this spell was cast for its primal cost, destroy all nonland permanents.

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.

Target player mills five cards. Draw a card for each card type among cards milled this way. (The card types are artifact, creature, enchantment, land, instant, planeswalker, sorcery, and tribal.)

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.)

When Thorn Tender enters, rouse 1, then put a +1/+1 counter on each creature you control. (Put a +1/+1 counter on a permanent you control. If it isn't a creature, tap it and it becomes a 0/0 creature in addition to its other types.)

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.

Thornwood Falls enters tapped.
When Thornwood Falls enters, you gain 1 life.
{T}: Add {G} or {U}.

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

Purge, then you may pay 2 life. If you do, purge again. (To purge, exile two cards that share a type from graveyards. If you do, draw a card.)

(Choose only one work as a sorcery to add its ability.)
When Those Lost to the Waves enters, search your library for an artifact card with mana value 3 or less, reveal it, put it into your hand, then shuffle.
{1}{W}: Fight the Current
Equipped creatures you control get +1/+1.
{3}{U}: Soul of the Sea
At the beginning of combat on your turn, you may have target noncreature artifact become a 3/3 artifact creature until end of turn.

Counter target instant or sorcery spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard. You may cast that spell for as long as it remains exiled and you may spend blue and black mana as though it were mana of any color to cast it.

Whenever a creature enters under an opponent's control, draw a card unless that player pays {1}.

When Thought Paradigm enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
Whenever you cast a sorcery spell, target player mills three cards.

Whenever an opponent draws a card except during their draw step, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Whenever an enchanted creature you control deals combat damage to a player, draw a card.

Whenever you draw a card, you may have target opponent exile the top card of their library face down.
You may look at and play cards exiled with Thought Siphon, and you may spend blue mana as though it were mana of any color to cast them.

When Thoughtgrinder enters, each player discards a card.
Unearth {1}{U}{B} ({1}{U}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)