msem-instigator

Creatures you control gain double strike until end of turn. Whenever a creature you control deals combat damage this turn, put a +1/+1 counter on it.

When Long Journey enters, exile target creature or planeswalker an opponent controls until Long Journey leaves the battlefield.

You draw X cards and you lose X life, where X is the number of different names among land cards in your graveyard.

Menace

Choose highest or lowest. Target opponent reveals their hand and discards a card with the chosen kind of mana value among the revealed nonland cards.

Archive 5 (As this enters, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
At the beginning of each upkeep, exile the top card of the archived library and your main library. You may cast those cards this turn and may spend mana as though it were mana of any color to cast them.

Flying, ward {2}
Whenever Faraway Albatross attacks, choose one —
• Faraway Albatross gets +1/+1 until end of turn for each spell you've cast this turn.
• Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Gain control of target creature until end of turn. Untap that creature. Until end of turn, it gets +1/+0 and gains haste.

Whenever you cast a spell, you may pay {1}. If you do, Wizened Tortle 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.)

Equipped creature gets +4/+2 and has first strike, vigilance, and trample.
Equip {3}

Counter target spell unless its controller pays {X}. If they do, you draw half X cards, rounded down.

Enchant player
At the beginning of enchanted player's end step, gain control of a permanent they control.

When Splinter of Creation enters, you may exile any number of land cards from your graveyard.
You may play lands exiled with Splinter of Creation.

Flash
Flying
Whenever this creature enters or you cast a spell during an opponent's turn, you may exile target non-Cat permanent you control, then return that permanent to the battlefield tapped under its owner's control.

Whenever Imisti, Elven Insurgent attacks, mill two cards. When you do, you may return target land card from your graveyard to your hand.
{X}{B}{G}: If Imisti has no +1/+1 counters on it, put X +1/+1 counters on Imisti. Activate only as a sorcery.

Runescale Brawler enters with three +1/+1 counters on it.
If damage would be dealt to Runescale Brawler while it has a +1/+1 counter on it, prevent that damage and remove a +1/+1 counter from Runescale Brawler.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)

Creatures you control get +1/+1 until end of turn.
Artifact creatures and Elementals you control get +1/+1 until end of turn.

Enchant creature
Enchanted creature can't block.
Whenever enchanted creature attacks an opponent, it gets +2/+2 until end of turn.

{3}, {T}, Sacrifice Punja Stick Trap: Punja Stick Trap deals 2 damage to target creature. Tap it.

Exile target artifact or enchantment. You gain 3 life.

Trample
{4}{R}{R}: Tortle Tinkerer explores. This ability costs {1} less to activate for each artifact you control. (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.)

When Bazaar Braggart enters, create a tapped Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

(Transform this if it's not attached to a creature. Pay {2}{W} as a sorcery to unattach it.)
Enchant creature you control
Slopestrider's Chariot's rider gets +1/+1 and has double strike.

Prowess
Each instant and sorcery card with mana value 3 or less in your hand has inscribe. The inscribe cost is equal to its mana cost increased by {1}{U/R}. (Pay that card's mana cost increased by {1}{U/R}: Exile that 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.)