Thalassia is an island in The Skull region of the Wushanko Isles. Sulphur is mined here to make gunpowder. The highest point of the island holds the khan's jade palace. The Khan of Thalassia is a cruel man named Tombi. During 'A Jade Frog in the Throat', you help Ling, a young assassin, kill him and replace him with another man.
- In A Friend Indeed, the player makes contact with a canny fisherman from Thalassia.
- In Troubled Waters, the player is trying to find a quicker route to Thalassia.
- In A Jade Frog in the Throat, The Assassin goes to Thalassia to depose Khan Tombi with the player's assistance.
- In A Joint Acquisition, the Whaler and the Biologist may send the player to a deserted port city near Thalassia that is surrounded by flying squid.
- The beast that the player encounters during the Deadliest Catch quest, Thalassus, is thought to be native to the waters surrounding this Island.