Attack on the Penetralium

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Next	Attack on the Atlantean Stronghold
Attack on the Penetralium
War	War for Earth
Date	July 25, 2017
Outcome	The Penetralium is sunk beneath the sea, Steppenwolf retrieves the first Mother Box Hippolyta warns Diana of the invasion
Combatants
Amazons
Steppenwolf Parademons
Commanders
Hippolyta
Steppenwolf
Casualties
Penthesilea Trigona Euboea Epione Venelia Philippus Many other Amazons
Many Parademons

" I have come to enlighten you to the Great Darkness! I will bathe in your fear!"
Daughters of Themyscira... Show him your fear!"
"WE HAVE NO FEAR!"

―Steppenwolf, Hippolyta and Amazon warriors^[src]

The Attack on the Penetralium was a conflict between Steppenwolf and the Amazons for the Mother Box hidden on the island.

Background

Steppenwolf discovered that Superman's death somehow managed to reactivate the three Mother Boxes. Willing to regain the favor of Darkseid, Steppenwolf traveled immediately to Earth with his army of Parademons to retrieve the Boxes and destroy the planet under the orders of his nephew.

Attack

Firstly, Steppenwolf went to Themyscira, where the first Mother Box was located. He appeared at the Penetralium where the Amazons stored the Mother Box. Despite the Amazons' efforts to escape with the Box or at least avoid Steppenwolf's destruction over the island, their defending ultimately failed. Queen Hippolyta attempted to escape with the Mother Box after sealing Steppenwolf inside the chamber, but Steppenwolf slaughters several Amazons and her horses after escaping from the chamber with some of his Parademons. He also escaped from the chamber and retrieved the Mother Box before Hippolyta and her Amazons could do anything, so Hippolyta contacted her daughter Diana to advise her of Steppenwolf's arrival to the Earth.

Aftermath

"We have to light the ancient warning fire."
"The fire has not burned for 5,000 years. Men won't know what it means."
"Men won't. She will."

―Hippolyta and Menalippe^[src]

At the Louvre, Diana watched a news report showing a signal fire burning at the Shrine of the Amazons and knew that it had been sent by her mother to warn of the impending invasion. She went to the Shrine of the Amazons, where she entered a cave system and discovered the story of Darkseid and his invasion of Earth using the Mother Boxes. Soon, she traveled to Gotham to tell Bruce Wayne about the incoming invasion and the story of the first invasion of Earth. Steppenwolf then teleported to Atlantis to retrieve the second Mother Box.