msem-instigator

Gain control of target creature with power X or less.

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.

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

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.

Return up to one target nonland permanent to its owner's hand. If you control a creature with flying, surveil 2.

Destroy target artifact.
Catalyze. (The next spell you cast this turn costs {1} less to cast.)

Choose one —
• Exile target player's graveyard.
• Target player sacrifices a creature.

Rapport — Whenever Memorial of Forgotten Heroes and at least one other creature you control become tapped, put a +1/+1 counter on one of those creatures.
{T}, Tap an untapped creature you control: Add one mana of any color.

Create X 1/1 black Goblin creature tokens. Gain control of target permanent with mana value X or less until end of turn. Untap it. It gains haste until end of turn.

Untap all nonland permanents you control.
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.)

Return target nonland permanent to its owner's hand. That player mills two cards.

Activated abilities you control cost up to {1} less to activate. This effect can't reduce the amount of mana an ability costs to activate to less than one mana.

Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

Deathtouch
Sacrifice a creature: Target player mills two cards.

Draw three cards, then put two cards from your hand on top of your library in any order.

Equipped creature gets +2/+0 and has haste.
Equip {2}

Whenever Merciless Bandit or another creature you control dies, each opponent loses 1 life and you gain 1 life.

Infiltrate (Whenever one or more attacking creatures you control aren't blocked, this creature gets +1/+1 until end of turn.)
Whenever Merciless Exiled deals combat damage to a player, scry 2.

{T}: Draw a card, then discard a card.

Counter target spell unless its controller pays {2}. If that spell targets you or a permanent you control, counter that spell instead.

Enchant creature
Enchanted creature can't be blocked.
{1}{R}: Enchanted creature gets +1/+0 until end of turn.

{3}{R}: Attacking creatures you control get +1/+0 until end of turn.

{T}: Add one mana of color.
{3}{G}, {T}: Audition for green. Activate only as a sorcery. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Warrior Role giving 3/2 and trample. Roles replace older ones.)

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Exile the top three cards of your library. Cast a spell with mana value X or less from among them without paying its mana cost.

Engage (This creature must be blocked each combat if able.)
{R}: Mettlesome Watchkeeper gets +1/+0 until end of turn.