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Erodious the Planet Killer (also known as Erodius) is the overarching antagonist of the 2021 Netflix science fantasy adventure series, Kid Cosmic, serving as the unseen overarching antagonist of Season 1, and the main antagonist of Season 2.
It is an evil alien entity that created the cosmic stones of power by destroying the home worlds of aliens whose natural abilities match the powers bestowed by each stone. It is also the archenemy of Queen Xhan and the Sole Survivors.
Not much is known about Erodious’s past, except that it started becoming a planet killer for reasons unknown.
Sometime before the events of the series, The Sole Survivoers tried to stop him from destroying their planets, but failed.
Erodious is first mentioned in the season finale “Kid Cosmic and the Day is Saved”, when Queen Xhan revealed that Erodious has destroyed her and the Sole Survivors’ planets.
6 months later, Erodious killed most of the Sole Survivors while fighting them, with Xhan being the only one to survive and forced to seek out the other 8 rings in addition to the 5 they had so as to stop Erodious.
Queen Xhan goes to help to Kid Cosmic, and she tells him and the crew that they need to collect right more stones in the galaxy to shop Erodious.
Erodious appears in “The Other Stones of Power”, where it is destroying a planet that had UPX and it's inhabitants while Fantos escapes back to his ship.
In “The Heist of Ice and Fire”, Erodious appears destroying a planet while Fantos tries to picture it, while picturing Jo.
In “The Soul Kroshing Loss”, Jo and Krosh go in the planet, Erodious, to try and stop it from destroying the Planets. However, Krosh and her clones betray Jo as they are about to leave Erodious, as Fantos vaporized them, much to his surprise as he introduces himself to Erodious while kidnapping Jo, who is stuck on a boulder.
In "The Fallen Hero", Erodious is sent through a portal to Mo's Oasis by Fantos, intending to destroy the area. Jo comes back with an armada that seeks to destroy Erodious to stop it from doing so.
In "The World Is Saved", Erodious successfully destroys Mo's Oasis, as well as Queen Xhan, and goes through another portal, created by Fantos, to Earth. Before it could destroy Earth, the Local Heroes find a way to destroy Erodious by using the stones that make then big, as well as the Goo Stone to seep into Erodious and stick together in a big mass, destroying Erodious from the inside.