Wingnut, Bat on the Belfry

Alliance — Whenever another creature you control enters, Wingnut gains your choice of flying, menace, or haste until end of turn.
Whenever Wingnut attacks, each other attacking creature gets +1/+0 until end of turn.

Ticked Off

Target creature gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Mountain

Casey Jones, Asphalt Hooligan

Double strike (This creature deals both first-strike and regular combat damage.)
{4}: Double Casey Jones's power until end of turn. Any player may activate this ability.

Mouser Foundry

When this artifact enters or leaves the battlefield, create a 1/1 colorless Robot artifact creature token.
{4}{R}, Sacrifice this artifact: It deals 3 damage to target creature.

Storm of Steel

Storm of Steel deals 2 damage to each of one or two targets.

Mutant Town Musicians

Trample
Alliance — Whenever another creature you control enters, this creature gets +1/+0 until end of turn.

Manhole Missile

Manhole Missile deals 3 damage to target creature. You may put a card from your hand on the bottom of your library. If you do, draw a card.

Mechanized Ninja Cavalry

When this creature enters, create a 1/1 colorless Robot artifact creature token.

Zog, Triceraton Castaway

Reach, trample
When Zog enters, target creature can't block this turn.
Mountaincycling {2} ({2}, Discard this card: Search your library for a Mountain card, reveal it, put it into your hand, then shuffle.)

Raph's Bravado

During your turn, attacking creatures get +1/+0.

Casey & Raph, Hotheads

When Casey & Raph enter, choose one or both. Each mode must target a different player.
• Target player exiles the top card of their library. Until that player's next end step, they may play that card without paying its mana cost.
• Target player creates two Treasure tokens.

Monster Mashup

Reach (This creature can block creatures with flying.)
Menace (This creature can't be blocked except by two or more creatures.)

Spicy Oatmeal Pizza

When this artifact enters, it deals 4 damage to any target and 3 damage to you.
{2}, {T}, Sacrifice this artifact: You gain 3 life.

Skateboard

When this Equipment enters, tap target permanent.
Equipped creature gets +1/+0 and has haste.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Casey Jones, Jury-Rig Justiciar

Haste
When Casey Jones enters, look at the top four cards of your library. You may reveal an artifact card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Raphael, Tough Turtle

Alliance — Whenever another creature you control enters, Raphael deals 1 damage to target opponent.

Raphael, Most Attitude

Menace (This creature can't be blocked except by two or more creatures.)
Alliance — Whenever another creature you control enters, you may exile the top card of your library.
Whenever Raphael attacks, until end of turn, you may play a card exiled with Raphael.

Mouser Attack!

Choose one —
• Create a 1/1 colorless Robot artifact creature token.
• Target creature gets +3/+0 and gains first strike until end of turn.

General Traag, Heart of Stone

Trample
When General Traag enters, you may sacrifice another artifact. When you do, General Traag deals 4 damage to target creature.

Definitely Not a Turtle

When this creature dies, look at the top six cards of your library. You may reveal a land or legendary Turtle card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Null Group Biological Assets

During your turn, this creature has first strike.
Whenever this creature attacks, you may discard a card. If you do, draw a card.

Raphael, Tag Team Tough

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Raphael deals combat damage to a player for the first time each turn, untap all attacking creatures. After this combat phase, there is an additional combat phase.