msem-instigator

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.)

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.)

Return two instant and/or sorcery cards at random from your graveyard to your hand. Exile Thoughts Reborn.

When Thoughtslick Engineer enters, each player discards a card at random.

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.)

This spell costs {2} more to cast for each target beyond the first.
Choose one or more —
• Counter target creature or planeswalker spell with mana value 4 or less.
• Exile target permanent you control, then return that card to the battlefield under your control.
• Target player draws two cards, then discards two cards and mills two cards.

Flash
When Threadripper Savant enters, put a stun counter on up to one target creature.

Flash
When Threadspinner enters, untap each enchanted permanent you control. Enchanted creatures you control get +1/+1 until end of turn.

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.

Enchant creature
Enchanted creature gets +3/+1.

Reveal the cards in your library. Target opponent chooses three nonland cards with different names from it. You put the chosen cards into your hand. Then shuffle.

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.

Wu Xing (Add effects based on the number of colors of mana spent to cast this spell.)
1 | Draw three cards.
5 | Add {W}{U}{B}{R}{G}. You can cast only one more spell this turn.

Target creature gets -3/-3 until end of turn. Its controller loses 3 life. You mill three cards.

When Threshing Sundew enters, merge up to one target creature card in your graveyard under it. Threshing Sundew has that card's abilities.
When Threshing Sundew dies, return all other cards merged with it to their owner's hand.

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