A Betazoid scientist of the 24th century, one of the group who concealed the Progenitors' technology, whose clue waits inside a manuscript held by the Eternal Gallery and Archive.
Marina Derex is first named in Whistlespeak, when Kovich supplies Burnham with the identities of the scientists behind the trail, and her clue is the subject of Labyrinths.
Derex wrote a work called Labyrinths of the Mind and placed the original in the Archive, a wandering library hidden within the Badlands. The book carries a device that draws its reader into a mental landscape. Burnham finds herself in a version of the Archive shaped by her own mind, guided by a figure who looks like Book.
The test cannot be solved by cleverness. It ends only when Burnham admits her fear of failure, the kind of self-knowledge Derex wanted in whoever went on to find the technology.