Storm Fleet Aerialist

Flying
Raid — Storm Fleet Aerialist enters with a +1/+1 counter on it if you attacked this turn.

Thriving Isle

Thriving Isle enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Malcolm, Keen-Eyed Navigator

Flying
Whenever one or more Pirates you control deal damage to your opponents, you create a Treasure token for each opponent dealt damage. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Partner (You can have two commanders if both have partner.)

Burdened Aerialist

When Burdened Aerialist enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Whenever you sacrifice a token, Burdened Aerialist gains flying until end of turn.

Corsair Captain

When Corsair Captain enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Other Pirates you control get +1/+1.

Prying Blade

Equipped creature gets +1/+0.
Whenever equipped creature deals combat damage to a player, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Convolute

Counter target spell unless its controller pays {4}.

Merchant Raiders

Whenever Merchant Raiders or another Pirate you control enters, tap up to one target creature. That creature doesn't untap during its controller's untap step for as long as you control Merchant Raiders.

Treasure Cove

(Transforms from Treasure Map.)
{T}: Add {C}.
{T}, Sacrifice a Treasure: Draw a card.

Treasure Map

{1}, {T}: Scry 1. Put a landmark counter on Treasure Map. Then if there are three or more landmark counters on it, remove those counters, transform Treasure Map, and create three Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Treasure Map // Treasure Cove

Island

Siren Stormtamer

Flying
{U}, Sacrifice Siren Stormtamer: Counter target spell or ability that targets you or a creature you control.

Storm Fleet Spy

Raid — When Storm Fleet Spy enters, if you attacked this turn, draw a card.

Admiral's Order

Raid — If you attacked this turn, you may pay {U} rather than pay this spell's mana cost.
Counter target spell.

Azure Fleet Admiral

When Azure Fleet Admiral enters, you become the monarch.
Azure Fleet Admiral can't be blocked by creatures the monarch controls.