msem-instigator

Menace
Whenever Masoh enters or attacks, each opponent that has more than four cards in hand discards cards equal to the difference. Then if you have fewer than four cards in hand, draw cards equal to the difference.

Whenever equipped creature attacks, it gets +1/+0 until end of turn for each other attacking creature.
Tap two untapped creatures you control: Equipped creature gains trample until end of turn.
Equip {3}

Creatures you control attacking cause abilities of that creature to trigger as though it entered.
{2}{R}{W}: Target creature gains vigilance and haste until end of turn. After this main phase, there is an additional combat phase followed by an additional main phase.

When Masterwork Archivist enters, search your library and/or command zone for a legendary card, reveal it, then put it into your hand or graveyard. If you searched your library this way, shuffle.
When Masterwork Archivist dies, you may draw a card.

Flash
Reach
Whenever Mattia enters or becomes tapped, put a +1/+1 counter on target creature you control.
{2}{G}, {T}: Target creature must be blocked this turn if able. Activate only as a sorcery.

Whenever you condemn a creature, each opponent sacrifices a creature.
{4}{B}: Judge target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Creatures you control lose poisonous and can't have or gain poisonous.
Snakes you control deal damage to players in the form of poison counters.

[+1]: Untap up to two target creatures and/or lands.
[–2]: Choose a color. Draw cards equal to the number of creatures you control of the chosen color.
[–7]: Reveal the top ten cards of your library. Put all creature and land cards revealed this way onto the battlefield and the rest into your hand.

Whenever Mawdryk, Endrison Warden or another nontoken Elf creature you control enters, create a 1/1 green Elf Druid creature token.
{B}{G}, Sacrifice two Elves: Destroy target non-Elf creature.

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
Recursive — As long as Mayar, Nullcrowned is a Curse, they have all nonrecursive abilities of other Curses and creatures with breach you control.
Pay 3 life: Target enchantment creature gains haste and menace until end of turn.

This spell can't be countered.
Flying, haste
Mayu, the Endless Flow gets +2/+2 for each spell you've cast this turn.

Indestructible (Damage and effects that say “destroy” don't destroy this creature.)

When Mechanical Mastodon enters, you may return another target permanent you control to its owner's hand.

Deploy 4 (As this enters, you may tap any number of other creatures you control with total power 4 or more.)
When Mechanical Tactician enters deployed, tap up to two target creatures an opponent controls. Those creatures don't untap during their controller's next untap step.

Mechanized Ideal gets +X/+Y, where X is the highest base power among other creatures you control and Y is the highest base toughness among other creatures you control.

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.

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

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.”

[+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.

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.)