The Second Astrotemple
The Second Astrotemple is located on an unnamed island in the Northern channel that splits Costrana. It was protected by the Cloud Giants of Lemrah until Balasar and the party found the island and were allowed to enter. Inside was an astrological model, a telescope, some blank books, and the chain of Balasar's search.
The temple disappeared after Balasar split the chain. Whether or not is can still be found is unknown.