Wonder Woman, Vol. 2 #11 (1987)

Challenge of the Gods, Part 2: Fire and Torment
As Diana makes her way through the Demon Lair beneath Paradise Island, her mother Hippolyta is visited by a strange vulture. Hippolyta decides she must make her way into the lair also to help her daughter, guided by the vulture. Diana defeats the Hydra and after a long battle with Echidna, she comes face to face with a strange woman dressed in similair armor as her own, who is also named Diana.
Release Date: 1987