A Boom Tube is an extra-dimensional portal that allows for instantaneous travel between two locations anywhere in the universe and beyond. It is used by the New Gods via their Mother Boxes to travel throughout space without the need for a ship.
Thousands of years ago, when Darkseid invaded Earth, he was defeated by the joint effort of the Amazons, Atlanteans, and Humans, with assistance from Yalan Gur of the Green Lantern Corps and the Old Gods. During the battle, his ships were destroyed, forcing him to flee through a boom tube summoned by his Apokoliptian Priests.
When Steppenwolf invaded Earth, he arrived from a boom tube opened in the vault in which the Amazons guarded one of the Mother Boxes the New God arrived with centuries ago. After defeating the Amazons and reclaiming the Mother Box, Steppenwolf summoned a boom tube, allowing him to escape.
In pursuit of the Mother Box held by the Atlanteans, Steppenwolf sent his Parademons to retrieve the Box secured in a vault beneath the ocean. When his soldiers failed, Steppenwolf appeared, defeating Aquaman and Mera, as well as multiple Atlantean Royal Guardsmen, before summoning another boom tube to return to his fortress in Russia.
Return of Superman
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