S3, E10: Struggling to heal from her injuries inflicted by Reign, Supergirl remains in a dreamlike state, unable to be reached. Mon-El recruits one of the Legion members, Brainiac-5 (guest star JESSE RATH), to try to bring her back. Meanwhile, Reign continues her rampage on the city, so the DEO teams up with the Legion of Super Heroes to try to stop her.