Pirate Seas is an Adventure Pack chapter in Skylanders: Spyro's Adventure and Skylanders: Giants that can only played by purchasing the Pirate Seas Adventure Pack. This expansion pack includes Terrafin, a pirate ship that unlocks the level, and two Magic Items, Hidden Treasure and Ghost Pirate Swords.
In the Wii version, once Kaos has been defeated, a Gillman with a pirate card minigame will appear next to the docked ship in the Ruins. The deck that you play with will always be random. The reward for playing the first time is 100 treasure. Afterwards, it is always 10 treasure.
The Skylanders are brought to the Pirate Seas by Jess LeGrand to help rid her home, the Coconut Islands, of the Pirates, who've taken over the town looking for treasures.