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.

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

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.

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

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

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

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

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

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 .

When a player casts a spell, sacrifice Standstill. If you do, each of that player's opponents draws three cards.

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

Counter target noncreature spell unless its controller pays .

( can be paid with either or 2 life.)
Target creature gets -5/-5 until end of turn.

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

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.

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

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."

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

: Target player exiles a card from his or her graveyard.
, Exile Relic of Progenitus: Exile all cards from all graveyards. Draw a card.

Flying
Creatures you control have "Whenever this creature becomes the target of a spell or ability for the first time in a turn, counter that spell or ability."