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

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Flash When this creature enters, tap target creature an opponent controls. It loses all abilities until end of turn.

Sacrifice this creature: Until end of turn, if a nontoken creature would enter and it wasn't cast, exile it instead.

As an additional cost to cast this spell, reveal a Merfolk card from your hand or pay {3}. When this creature enters, draw a card.

Flash Flying When this creature enters, choose up to one target creature spell or planeswalker spell. Its owner puts it on their choice of the top or bottom of their library. Evoke—Exile a blue card from your hand.

Svyelun has indestructible as long as you control at least two other Merfolk. Whenever Svyelun attacks, draw a card. Other Merfolk you control have ward {1}. (Whenever another Merfolk you control becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)

Kicker {1} (You may pay an additional {1} as you cast this spell.) When this creature enters, if it was kicked, target land becomes an Island for as long as this creature remains on the battlefield. This creature gets +1/+1 as long as an opponent controls an Island.

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

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost. Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Choose one — • Counter target artifact spell. • Return target artifact to its owner's hand.

As this land enters, choose a creature type. {T}: Add {C}. {T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

({T}: Add {U}.)

{T}: Add {U}. {U}, {T}: Untap target legendary permanent.

{T}: Add {C}. {1}: This land becomes a 2/2 creature with all creature types until end of turn. It's still a land.