msem-instigator

Whenever another creature you control enters, you may pay {2}. If you do, judge that creature. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

{1}, Sacrifice Martyr of the Work: Purge. (Exile two cards that share a type from graveyards. If you do, draw a card.)

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{1}, {T}: Look at the top card of your library. You may put the card back or into your graveyard.

Art of war — At the beginning of your end step, if Masamori Ranger dealt damage to an opponent this turn, search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

First strike
When Masha Ritualist enters or whenever you cast a spell, if {B}{G} was spent to cast it, return target creature card with mana value 3 or less from a graveyard to the battlefield under your control. Put a +1/+1 counter on Masha Ritualist.

Sacrifice a creature: Put a +1/+1 counter on Masked Assailant. It gains menace until end of turn. Activate only as a sorcery.

Once each turn, when you activate a nonmana ability, you may have Masked Servant get +1/+1 until end of turn.
{2}{W}: Untap target creature.

When Mass Orator enters, if it isn't a token, populate. (Create a token that's a copy of a creature token you control.)
Creature tokens you control get +1/+1.

When Master Chef enters, create a 0/1 green Plant creature token.
Sacrifice a Plant: You gain 3 life.

When Master Negotiator enters, you may gain control of target nonland permanent an opponent controls with mana value 2 or less. If you do, its controller may draw a card. Otherwise, you draw a card.

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever Master of Ancient Ways mentors a creature, that creature gains double strike until end of turn.

Other creatures you control get +0/+1.

Flash
When Master of Disorientation enters, you may choose new targets for target instant or sorcery spell. Then proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Whenever a nonbasic nontoken land enters under an opponent's control, create a tapped colorless land token named Fading Rift with “{T}, Sacrifice this land: Add one mana of any color.”

You can't cast more than one spell each turn.
Whenever you cast a spell, draw a card.

Whenever an artifact you control enters, Master of Munitions deals 1 damage to each opponent.

When Master of the Glen enters, create a 2/2 green Wolf Elemental creature token.
Elementals you control have trample.

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.

Equipment spells you cast cost {1} less to cast.
Equip abilities you activate cost {1} less.

When Matron of Machines dies, put a +1/+1 counter on up to one target creature.
{3}{W}, Exile Matron of Machines from your graveyard: Create two 1/1 colorless Construct artifact creature tokens. Activate only as a sorcery.

Menace
Whenever one or more creature cards leave your graveyard, put a +1/+1 counter on Mausoleum Resident. It gains lifelink until end of turn.

Reach
When Mawdryk's Harrier enters, look at the top six cards of your library. You may put an Elf card with lesser mana value from among them onto the battlefield. Put the rest on the bottom of your library in a random order.
Other Elves you control get +1/+1.

When Meadow Songstress enters, conjure three cards named Meadow Songstress and shuffle them into your main library.
Whenever a nontoken creature you control enters, if it shares a name with one or more other creatures you control, draw a card.

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.)

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