which third annual Arrowverse crossover event did "Medusa"  features
Medusa (Supergirl) "Medusa" is the eighth episode of the second season from The CW television series "Supergirl", which aired on November 21, 2016. The episode features a minor tie-in with the Arrowverse crossover event "Invasion!"
The Coming of Atlas "The Coming of Atlas" is a comic book story arc, from DC Comics, by writer James Robinson and artists Renato Guedes and José Wilson Magalháes, featuring Superman. This is Robinson's first story arc on the "Superman" title, as ongoing writer after Kurt Busiek's departure. This, as well as Geoff Johns's "Brainiac" arc on "Action Comics", lead to their planned narrative unification on "Action Comics", "Superman" and "Supergirl" in "".