Lord of Atlantis

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

Merfolk Traders

When Merfolk Traders enters, draw a card, then discard a card.

Whenever Saprazzan Heir becomes blocked, you may draw three cards.

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Draw two cards.

{T}: Target land becomes an Island until end of turn.

When Vodalian Merchant enters, draw a card, then discard a card.

{U}, {T}, Discard a card: Return target creature to its owner's hand.

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Target player draws two cards.
Flashback—{1}{U}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)