Thusa was a female humanoid of an unknown species whose members reproduced and/or resurrected themselves by touching someone else to create an infantile clone of themselves.
In 2381, Thusa, a guide, led Dr. T'Ana and Lt. jg Sam Rutherford through a cave on Balkus 9 to obtain some medicinal ferns. As she began to pick the ferns, Rutherford's tricorder registered something and he suggested that they should probably leave. Thusa dismissed his warning, explaining that the Grafflax haven't lived in these caves for generations. She was proven wrong when the Grafflax broke the surface, grabbed her with its maw and tossed her against a wall. After Rutherford and T'Ana quickly drove it off with their phasers, they noticed that Thusa landed on a stalagtite. As T'Ana tried to stabilize her, Thusa declared that her body was gone and laid her hand on Rutherford's face, transferring her essence into him, before she died. (LD: "Caves")
Thusa was voiced by Dawnn Lewis.