msem-instigator

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.

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.

(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.

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 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.

Enchant creature
Enchanted creature gets +3/+1.

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.

Each creature you control enters with an additional +1/+1 counter on it.
Each planeswalker you control enters with an additional loyalty counter on it.

Whenever a permanent an opponent controls becomes the target of a spell you control, put a progress counter on Throne of the West.
[PROGRESS 2+] {T}: Gain control of target permanent until end of turn. Untap it. It gains haste until end of turn.
[PROGRESS 5+] You can't lose control of permanents.

When Through the Dust enters, it becomes an Aura with enchant creature. Reveal the top seven cards of your library, put a creature card revealed this way onto the battlefield and attach Through the Dust to it. Then put the rest on the bottom of your library in any order. When Through the Dust is no longer on the battlefield, enchanted creature's controller sacrifices it.
Mirage {1}{U}{U}{U} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Creature tokens you control get +1/+1.
Whenever Thyra, Winter's Warden enters or attacks, you may pay {1}{G/W}. If you do, create Bruga, a legendary 2/2 green and white Wolf creature token.

Enchant creature
When Til Death enters, exile target creature an opponent controls other than enchanted creature until Til Death leaves the battlefield.
Enchanted creature has defender.

Instant and sorcery spells you control have leitmotif. (Exile that spell as it resolves if you cast it from your hand. When you next cast a spell that shares a color with that card, you may cast it from exile without paying its mana cost.)

{16}, {T}: Time Cube gains “At the beginning of your end step, if it's not an extra turn, take three extra turns after this one” and loses this ability.

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.

First mate — Each nonland card in your starting deck is an artifact, a Pirate, or has “artifact,” “Treasure,” or “Pirate” in its printed rules text. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Whenever Tinbeard of the Brine attacks, each opponent loses X life and you gain X life, where X is the number of artifacts you control plus the number of Pirates you control.

At the beginning of combat on your turn, tap Tinchor, put two +1/+1 counters on him, you draw a card, and you lose 1 life.
When Tinchor dies, put his counters on target Human you control.

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.

Your opponents can't search libraries unless they pay {2}.
[+2]: If an opponent has more life than you, you gain 2 life.
[0]: If an opponent controls more creatures than you, you create two 1/1 white Gnome creature tokens.
[–4]: Search your library for a creature card with mana value 2, put it onto the battlefield, then shuffle.

Flash
Enchant creature
Enchanted creature gets +1/+1 and has first strike.

This spell costs {2} less to cast if you've cast another spell this turn.
Enchant creature
When Tire Out enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Nonstoried creatures lose all abilities and have base power and toughness 1/1. (Enchantments and legendary permanents are storied.)

Enchant creature without flying
Enchanted creature gets +10/+0 and attacks each combat if able.

When Titou Louoe, Bayou Shaman enters, create a blue Aura Curse enchantment token named Curse of Impotence attached to target player. The token has enchant player and “Creatures enchanted player controls get -1/-0.”