A 32nd-century Starfleet admiral whose Tal symbiont passed to Gray and then to Adira, carrying the memories that led Discovery to Starfleet.
Senna Tal is a Starfleet admiral whose transmission from Earth Michael Burnham finds in People of Earth. By the time Discovery reaches Earth he is dead, and the young human Adira is identified as the host of his Trill symbiont.
In Forget Me Not, Adira learns that when Senna died the Tal symbiont passed to Gray, Adira's Trill partner, and then to Adira after Gray was killed. In Die Trying, Adira uses Senna's memories to guide Discovery to the hidden Starfleet headquarters.