msem-instigator

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.)

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.)

(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 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.)

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.

Haste
At the beginning of combat on your turn, create two nonlegendary token copies of Thrice-Clawed Troika. Then for each creature token created this way, create token copies of each permanent attached to Thrice-Clawed Troika and attach them to that creature token. Exile all tokens created this way at end of combat.

Whenever Thrinax Sporemother or another nontoken creature you control dies, create a 1/1 green Saproling creature token.
Whenever a creature card is exiled from your graveyard, create a 1/1 green Saproling creature token.

The next creature spell you cast this turn may be cast as though it had flash and costs {1} less to cast. If it entering the battlefield causes a triggered ability of it to trigger, that ability triggers an additional time.

Each player sacrifices a creature with mana value X or greater.
Return up to one target creature card with mana value X or less from your graveyard to the battlefield.

Augmented — When you cast this spell, if it's your turn and you've spent {W}{U}{B}{R}{G} to cast spells this turn, copy it twice. You may choose new targets for the copies.
Thunder Road deals 3 damage to any target. You gain 3 life.

Whenever Thundering Towershell attacks, return a creature card with mana value 5 or less from a graveyard to the battlefield under your control. Trigger a death knell of that creature.

Vigilance, menace, trample, haste
Whenever you cast a spell, you may have Thunderous Avarice consume. If you do, put a +1/+1 counter on it. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
Whenever an opponent casts a spell, they may have Thunderous Avarice consume. If they don't, put a +1/+1 counter on it.

Choose target creature you control and target creature you don't control. Flip a coin. If the coin comes up heads, put one of those creatures on top of its owner's library. Otherwise, put both of them on top of their owners' libraries.

Destroy target non-Xirix permanent. If that permanent had mana value 6 or greater, take an extra turn after this one.

Whenever a creature you control enters, Timid Thunderhorn gets +X/+X until end of turn, where X is that creature's power.

First strike
If one or more creature tokens would be created under your control, for each of those tokens, you may create three 2/2 green Cat Warrior creature tokens instead.

When Tinker Tantrum enters and at the beginning of your upkeep, you may sacrifice an artifact. If you do, reveal cards from the top of your library until you reveal an artifact card with mana value X or less, where X is 1 plus the sacrificed artifact's mana value. Put that card onto the battlefield and the rest on the bottom of your library in a random order.

Vigilance
Permanent spells you cast cost {1} less to cast for each 1 damage Tireless Explorer has dealt to players this turn.

Return target creature card from your graveyard to the battlefield.

Reach
You may have other creatures you control enter as a copy of any creature card in a graveyard with equal or lesser mana value.

Primal {5}{U}{R} (During your turn, you may cast this spell for {5}{U}{R} instead of playing a land.)
Each player discards their hand, then draws seven cards. If this spell was cast for its primal cost, draw cards equal to the number of cards your opponents discarded this way.

You may put cards with mana value 2 or less that permanents you control explore into your hand as though they were lands. (You won't get the counter if you do.)
Whenever Torch of Those Underfoot attacks, it explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)