The Twin Seas are, in fact, a single waterway divided only by a narrow neck that separates the western and eastern halves of Sanctuary. The northerly sea acts as a barrier between Aranoch to the west and Kehjistan to the east. The southerly sea leads into the Great Ocean, and is the location of the Skovos Isles.
Violent storms sometimes occur in the Seas, and are sailed by pirates. In the past, these pirates lay siege to Tran Athulua. Pirates remain an issue in the present. To this end, sailors from Lut Gholein distill the waters of the Twin Seas and apply the bright blue mixture to their sails in order to blend in and avoid detection by pirates.