Power Girl faces her biggest personal challenge when the JLE journeys to the underworld of Greek mythology to try to stop the vengeful goddess Echidna from destroying mankind. Wonder Woman makes an appearance.
The team is transported to a dark, cavernous, downward-leading place Wonder Woman refers to as "The Waiting Room". It is there that Flash begins to fall victim to hallucinations when the team is suddenly attacked by Cerberus, the giant three-headed dog of Greek myth. Wonder Woman confronts the dog while the rest of the group continue onward. Next, Flash vanishes, followed by Elongated Man, Aquaman and Green Lantern, all of them victims of tempting female apparitions. Metamorpho is encased in solid stone from the neck down and immobilized, leaving only the women in the group to press on.
The group, consisting of Doctor Light, Power Girl, Crimson Fox and Wonder Woman encounter the missing heroes and discover they have been turned into animals. A short while later, Doctor Light suffers a panic attack brought on by her fear of the dark and claustrophobia. Instinctively, her powers kick in and the cavern is suddenly engulfed in bright light. The sudden burst of light reveals the face of their true foe, Echidna, half-woman, half monster-serpent and mother of all Greek mythological monsters, as well as goddess of the underworld. Wonder Woman pounces on Echidna, but is trapped in her thick, strong, endless coils before being encased in the cavern wall. Crimson Fox, whose powers draw on pheromones and seductive feminine energy, is enthralled by Echidna and rendered powerless and immobilized; only Power Girl is left standing.
Echidna, sensing an affinity with Power Girl tries to convince her to join forces and become a vessel for Echidna's rage against the world of mortal men. Power Girl rejects her offer and attacks, causing the cave to tremble fiercely. The JLE manages to evacuate to the surface, seemingly unharmed. Moments later, Power Girl also emerges. She reveals that Echidna agreed to leave the team and the surface world alone in exchange for Power Girl agreeing to return to Echidna's underworld once a year as her student, with the purpose of reintroducing Echidna's earth-mother energies to her fellow super-heroines as well as the world of mortals.