Incremental Growth

Put a +1/+1 counter on target creature, two +1/+1 counters on another target creature, and three +1/+1 counters on a third target creature.

Reclaiming Vines

Destroy target artifact, enchantment, or land.

Natural Connection

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Sauroform Hybrid

{4}{G}{G}: Adapt 4. (If this creature has no +1/+1 counters on it, put four +1/+1 counters on it.)

Harmonize

Jade Bearer

When Jade Bearer enters, put a +1/+1 counter on another target Merfolk you control.

Verdant Haven

Enchant land
When Verdant Haven enters, you gain 2 life.
Whenever enchanted land is tapped for mana, its controller adds an additional one mana of any color.

Overgrown Battlement

Defender
{T}: Add {G} for each creature you control with defender.

Jadecraft Artisan

When Jadecraft Artisan enters, target creature gets +2/+2 until end of turn.

Wall of Runes

Defender (This creature can't attack.)
When Wall of Runes enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Aquitect's Will

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Merfolk Mistbinder

Merrow Levitator

{T}: Target creature gains flying until end of turn.
Whenever you cast a blue spell, you may untap Merrow Levitator.

Island

Jungleborn Pioneer

When Jungleborn Pioneer enters, create a 1/1 blue Merfolk creature token with hexproof. (It can't be the target of spells or abilities your opponents control.)

Caustic Caterpillar

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

Swell of Growth

Target creature gets +2/+2 until end of turn. You may put a land card from your hand onto the battlefield.

Larger Than Life

Target creature gets +4/+4 and gains trample until end of turn.

Aggressive Urge

Target creature gets +1/+1 until end of turn.
Draw a card.

Negate

Stony Strength

Put a +1/+1 counter on target creature you control. Untap that creature.

Deeproot Warrior

Whenever Deeproot Warrior becomes blocked, it gets +1/+1 until end of turn.

River Sneak

River Sneak can't be blocked.
Whenever another Merfolk you control enters, River Sneak gets +1/+1 until end of turn.

Courage in Crisis

Put a +1/+1 counter on target creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Wind Strider

Flash (You may cast this spell any time you could cast an instant.)
Flying

Kiora's Dambreaker

When Kiora's Dambreaker enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Vorel of the Hull Clade

{G}{U}, {T}: Double the number of each kind of counter on target artifact, creature, or land.

Centaur Nurturer

When Centaur Nurturer enters, you gain 3 life.
{T}: Add one mana of any color.

Tishana's Wayfinder

When Tishana's Wayfinder enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Earthen Arms

Put two +1/+1 counters on target permanent.
Awaken 4—{6}{G} (If you cast this spell for {6}{G}, also put four +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Coral Commando

Thornado

Destroy target creature with flying.
Cycling {1}{G} ({1}{G}, Discard this card: Draw a card.)

Steeple Creeper

{3}{U}: Steeple Creeper gains flying until end of turn.

Protective Bubble

Enchant creature
Enchanted creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)

Clutch of Currents

Return target creature to its owner's hand.
Awaken 3—{4}{U} (If you cast this spell for {4}{U}, also put three +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Forest

Skitter Eel

{2}{U}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)

Streambed Aquitects

{T}: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn. (It can't be blocked as long as defending player controls an Island.)
{T}: Target land becomes an Island until end of turn.

Might of the Masses

Target creature gets +1/+1 until end of turn for each creature you control.

Giltgrove Stalker

Giltgrove Stalker can't be blocked by creatures with power 2 or less.

Kiora's Follower

Mist-Cloaked Herald

Contentious Plan

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

Overcome

Creatures you control get +2/+2 and gain trample until end of turn. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)

Fertile Ground

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional one mana of any color.

Wall of Mist

Cloud Manta

Wardscale Crocodile

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Biogenic Upgrade

Distribute three +1/+1 counters among one, two, or three target creatures, then double the number of +1/+1 counters on each of those creatures.

Enclave Elite

Multikicker {1}{U} (You may pay an additional {1}{U} any number of times as you cast this spell.)
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Enclave Elite enters with a +1/+1 counter on it for each time it was kicked.

Cached Defenses

Bolster 3. (Choose a creature with the least toughness among creatures you control and put three +1/+1 counters on it.)

Zephyr Sprite

Coral Merfolk

Jungle Delver

{3}{G}: Put a +1/+1 counter on Jungle Delver.

Jade Guardian

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
When Jade Guardian enters, put a +1/+1 counter on target Merfolk you control.

Kasmina's Transmutation

Enchant creature
Enchanted creature loses all abilities and has base power and toughness 1/1.

Quest for the Gemblades

Whenever a creature you control deals combat damage to a creature, you may put a quest counter on Quest for the Gemblades.
Remove a quest counter from Quest for the Gemblades and sacrifice it: Put four +1/+1 counters on target creature.

Stealth Mission

Put two +1/+1 counters on target creature you control. That creature can't be blocked this turn.

Regenesis

Return up to two target permanent cards from your graveyard to your hand.

Tideshaper Mystic

{T}: Target land becomes the basic land type of your choice until end of turn. Activate only during your turn.

Merfolk of the Depths

Flash (You may cast this spell any time you could cast an instant.)

Sylvan Brushstrider

When Sylvan Brushstrider enters, you gain 2 life.

Trollbred Guardian

{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has trample.