Level up
LEVEL 2-3|Flying|3/3
LEVEL 4+|Flying
Other merfolk creatures you control gets +1/+1|4/4

: Add to your mana pool.
, Sacrifice Wasteland: Destroy target nonbasic land.

: Add to your mana pool.
: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.

At the beginning of your upkeep, you may put a charge counter on Æther Vial.
: You may put a creature card with converted mana cost equal to the number of charge counters on Æther Vial from your hand onto the battlefield.

You may pay 1 life and exile a blue card from your hand rather than pay Force of Will's mana cost.
Counter target spell.

Other Merfolk creatures get +1/+1 and have islandwalk.

Sacrifice Cursecatcher: Counter target instant or sorcery spell unless its controller pays .

As an additional cost to cast Silvergill Adept, reveal a Merfolk card from your hand or pay .
When Silvergill Adept enters the battlefield, draw a card.

You may have Phantasmal Image enter the battlefield as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it gains "When this creature becomes the target of a spell or ability, sacrifice it."

Other Merfolk creatures you control get +1/+1.
Whenever you cast a Merfolk spell, you may tap or untap target permanent.

Counter target noncreature spell unless its controller pays .

Flash
Flying
When Spellstutter Sprite enters the battlefield, counter target spell with converted mana cost X or less, where X is the number of Faeries you control.

You may return an Island you control to its owner's hand rather than pay Daze's mana cost.
Counter target spell unless its controller pays .

Whenever equipped creature deals combat damage, put two charge counters on Umezawa's Jitte.
Remove a charge counter from Umezawa's Jitte: Choose one - Equipped creature gets +2/+2 until end of turn; or target creature gets -1/-1 until end of turn; or you gain 2 life.
Equip

Flying
Discard Faerie Macabre: Exile up to two target cards from graveyards.

Flying
When Sower of Temptation enters the battlefield, gain control of target creature for as long as Sower of Temptation remains on the battlefield.

Choose one - Counter target red spell; or destroy target red permanent.

If an opponent controls a Forest and you control an Island, you may cast Submerge without paying its mana cost.
Put target creature on top of its owner's library.

, Sacrifice Tormod's Crypt: Exile all cards from target player's graveyard.