You may have Mercurial Pretender enter the battlefield as a copy of a creature you control, except it has ": Return this creature to its owner's hand."

Until end of turn, target nonland permanent loses all abilities and becomes your choice of a blue Frog creature with base power and toughness 1/1 or a blue Octopus creature with base power and toughness 4/4.

Outlast (, : Put a +1/+1 counter on this creature. Outlast only as a sorcery.)

Each creature you control with a +1/+1 counter on it has deathtouch.

: Destroy target creature with islandwalk.

Whenever a creature you control explores, Merfolk Cave-Diver gets +1/+0 until end of turn and can't be blocked this turn.

Flying

Whenever you cast a kicked spell, scry 2.

, : Target player mills two cards.

When Merfolk Observer enters the battlefield, look at the top card of target player's library.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)

Flying

When Merfolk Skydiver enters the battlefield, put a +1/+1 counter on target creature you control.

: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Other Merfolk creatures you control get +1/+1.

: Target Merfolk creature can't be blocked this turn.

: Switch target creature's power and toughness until end of turn.

Flash

When Merfolk Trickster enters the battlefield, tap target creature an opponent controls. It loses all abilities until end of turn.

Flying

Whenever Merfolk Windrobber deals combat damage to a player, that player mills a card. (They put the top card of their library into their graveyard.)

Sacrifice Merfolk Windrobber: Draw a card. Activate only if an opponent has eight or more cards in their graveyard.

Whenever one or more Halflings you control attack a player, create a Food token. (It's an artifact with ", , Sacrifice this artifact: You gain 3 life.")

Merieke Ri Berit doesn't untap during your untap step.

: Gain control of target creature for as long as you control Merieke Ri Berit. When Merieke Ri Berit leaves the battlefield or becomes untapped, destroy that creature. It can't be regenerated.

At the beginning of your end step, untap all Merfolk you control.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

When Merrow Harbinger enters the battlefield, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.

Other Merfolk creatures you control get +1/+1.

Whenever you cast a Merfolk spell, you may tap or untap target permanent.

When Merrow Witsniper enters the battlefield, target player mills a card.

Haste

Merry, Esquire of Rohan has first strike as long as it's equipped.

Whenever you attack with Merry and another legendary creature, draw a card.

Visit — Creatures you control with power 2 or less gain horsemanship until end of turn. (They can't be blocked except by creatures with horsemanship.)

Lights — 2, 6

Enchant creature

Merseine enters the battlefield with three net counters on it.

Enchanted creature doesn't untap during its controller's untap step if Merseine has a net counter on it.

Pay enchanted creature's mana cost: Remove a net counter from Merseine. Only the controller of the enchanted creature may activate this ability.

Stand up, Flap your arms, Cluck like a chicken: Mesa Chicken gains flying until end of turn.

Flying

: Mesa Falcon gets +0/+1 until end of turn.

Flying; banding (Any creatures with banding, and up to one without, can attack in a band. Bands are blocked as a group. If any creatures with banding you control are blocking or being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.)

When Mesmeric Fiend enters the battlefield, target opponent reveals their hand and you choose a nonland card from it. Exile that card.

When Mesmeric Fiend leaves the battlefield, return the exiled card to its owner's hand.

Whenever a permanent becomes untapped, that permanent's controller mills a card.

Cumulative upkeep (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

, Discard a card: Draw a card.

Enchant creature

When Mesmerizing Dose enters the battlefield, tap enchanted creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Enchanted creature doesn't untap during its controller's untap step.

Flying

When Messenger Falcons enters the battlefield, draw a card.

Enchant creature

Enchanted creature has trample and haste.

Tap all artifacts.

As Metallic Mimic enters the battlefield, choose a creature type.

Metallic Mimic is the chosen type in addition to its other types.

Each other creature you control of the chosen type enters the battlefield with an additional +1/+1 counter on it.

Whenever you cast an instant or sorcery spell, create an X/X colorless Construct artifact creature token, where X is that spell's mana value.

, Exile Metallurgic Summonings: Return all instant and sorcery cards from your graveyard to your hand. Activate only if you control six or more artifacts.

This spell costs less to cast, where X is the total mana value of noncreature artifacts you control.

Sacrifice two artifacts: Return Metalwork Colossus from your graveyard to your hand.

Enchant creature

As Metamorphic Alteration enters the battlefield, choose a creature.

Enchanted creature is a copy of the chosen creature.

Threshold — Metamorphic Wurm gets +4/+4 as long as seven or more cards are in your graveyard.

As an additional cost to cast this spell, sacrifice a creature.

Add X mana of any one color, where X is 1 plus the sacrificed creature's mana value. Spend this mana only to cast creature spells.

Metathran Elite can't be blocked as long as it's enchanted.

Flying

Metathran Transport can't be blocked by blue creatures.

: Target creature becomes blue until end of turn.

Meteor Blast deals 4 damage to each of X targets.

When Meteor Golem enters the battlefield, destroy target nonland permanent an opponent controls.

, Discard two cards at random: Meteor Storm deals 4 damage to any target.

Equipped creature gets +4/+0 and has trample.

Equip

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

(: Add or .)

Meticulous Archive enters the battlefield tapped.

When Meticulous Archive enters the battlefield, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

When a spell or ability an opponent controls causes you to discard Metrognome, create four 1/1 colorless Gnome artifact creature tokens.

, : Create a 1/1 colorless Gnome artifact creature token.