msem-instigator

Artifact vision (Whenever this or another artifact you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Mechanomind Researcher envisions an artifact card, put a +1/+1 counter on it.

Flying
{2/B}{2/B}, {T}, Sacrifice Meddling Gargoyle: Target opponent reveals their hand. You choose a nonland card from it. That player discards that card. Activate only as a sorcery.

When Medical Mask enters, prevent the next 3 damage that would be dealt to any target this turn.
{4}, Sacrifice Medical Mask: Prevent the next 6 damage that would be dealt to any target this turn.

I, II — Put a +1/+1 counter on target creature you control.
Discovery — Creatures you control with +1/+1 counters on them have lifelink.

Equipped creature gets +1/+1.
Whenever equipped creature becomes the target of a spell, you gain 3 life.
Equip {4}

Trample
Enchantment spells and Aurashaper spells you cast cost {1} less to cast.
Whenever another enchantment you control enters, draw a card.

At the beginning of combat on your turn, if you cast an enchantment spell, an instant spell, and a sorcery spell this turn, create two 3/3 red Shark enchantment creature tokens. You may have any number of those tokens gain haste. If you do, sacrifice the tokens you chose at end of combat.

Colossal 4—{5}{U}{U}{U} (You may cast this for its colossal cost to have it enter with four +1/+1 counters; or pay {5}{U}{U}{U} as a sorcery: Put four +1/+1 counters on it if it has none.)
Whenever Megalokraken enters or attacks, reveal the top X cards of your library, where X is Megalokraken's power. You may cast a noncreature spell with mana value X or less from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

Lifelink, menace

Whenever a player discards a card, you may draw a card and put a loyalty counter on Mei Liva, the Broken.
[0]: Target permanent's controller sacrifices it unless they discard two cards.
[–1]: Each opponent loses X life and you gain X life, where X is the number of cards in your hand.
[–3]: Target player chooses a card in their hand, then discards the rest.

[+1]: Search each player's graveyard, hand, and library for any number of cards with the same name as target nonbasic card in a graveyard and exile them. Then each player shuffles.
[–2]: Each player draws two cards, then each opponent exiles two cards at random from their hand.
[–5]: You may cast a card exiled with Mei Liva without paying its mana cost.

[+2]: Each opponent loses 2 life. Scry 2.
[–3]: Return target creature to its owner's hand. That player discards a card.
[–6]: You get an emblem with “Whenever a player discards a card, you may cast it without paying its mana cost.”

Codex — Unraveling; Unraveling; Unrelenting; Unrelenting; Mindrip; Swipe Secrets. (As this enters, conjure its contents into a shuffled face-up additional library.)
Flash
When Mei's Collection enters, draw a card from its codex.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature dies, put a +1/+1 counter on Mei's Collector.

Whenever Mei's Student deals combat damage to a player, fateseal 1, then scry 1. (Look at the top card of an opponent's library, then you may put it on the bottom.)

Flying
When Mei's Understudy enters, if you control another Actor, draw a card.

[+1]: Draw a card unless an opponent discards a card.
[–3]: Gain control of target creature until the end of your next turn.
[–6]: Choose up to four cards in graveyards. You may play those cards without paying their mana costs.

Each opponent loses 2 life and you gain 2 life. You mill two cards.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

Lifelink
Creatures can't be sacrificed.
{1}: Add {G}, {U}, or {R}. Spend this mana only to cast a Human spell.

Meletian Trireme can't be blocked by creatures with power 2 or less.
Whenever Meletian Trireme enters or deals combat damage to a player or planeswalker, scry 1, then draw a card.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

When Meletis Oracle enters, scry 1, then draw a card.

Heroic — Whenever you cast a spell that targets Meletis Stargazer, scry 2.
{T}: Look at the top card of your library. If it's a permanent card with mana value 3 or less, you may reveal it and put it into your hand.

Flash
Flying
When Meletis Stratomancer enters, target creature an opponent controls gets -2/-0 until end of turn.

Melodae, the Favored can't be blocked by black creatures.
If Melodae would be destroyed, instead sacrifice a creature and Melodae gains indestructible until end of turn.

Whenever Melodious Musician attacks, tap target creature an opponent controls.