Legendary Planet

The Legendary Planets, known in Japan as the Planet Series, are a major plot point from the Yu-Gi-Oh! GX manga, which were created by the father of Aster Phoenix and stolen by Tragoedia. The series consists of nine powerful cards, each analogous to one of the planets in the solar system at the time of the manga's first release. The cards are named accordingly, with all of them possessing some sort of reference to their respective planets within their names and card arts. Unlike similar series of cards, like the Egyptian Gods or the Sacred Beasts, the Legendary Planets do not appear to have any sort of inherent magical or ancient quality to them; they are simply powerful cards used by the protagonist Jaden Yuki and various antagonists in league with Tragoedia, who goes to certain lengths to retrieve the cards from minions who fail him. As of the most recent chapter, all nine cards have been revealed.

In the OCG/Japanese manga, the Planet Series naming convention is The (adjective) PLANET (with the exception of "Terra Firma", who's OCG name is "Elemental Hero The Earth"). The words are written in upper case English. In the English manga, the word "the" is removed, whereas in the TCG, with the exception of "Venus" (who is just called "Splendid Venus"), the names are kept the same as the OCG name, minus the capitalization. "Terra Firma" was used in place of "The Earth" for unknown reasons.

In the GX Manga, Alexis Rhodes has faced many of the revealed Planet cards, and she has lost each match when she faced one. In her match with Jaden Yuki, she fought "Terra Firma". Against David Rabb, she lost to the "The Big Saturn". And she also lost to Reggie MacKenzie, who used "Splendid Venus". She later faced Aster Phoenix in the American vs Japanese one-on-one matches, and lost to his newly obtained Planet "The Grand Jupiter". The fifth monster of this Archetype, "The Tyrant Neptune" is used by Jim Crocodile Cook in his duel against Atticus Rhodes. But unlike his sister, Atticus won his match against a Legendary Planet. The sixth monster, "The Despair Uranus" is used by Adrian Gecko against Jaden Yuki. "The Tripping Mercury", the seventh Planet monster is used by Jesse Anderson to defeat Syrus Truesdale. The eighth planet card "The Blazing Mars" is used by Axel Brodie against Chazz Princeton, but that duel hasn't finished yet.

In chapter 54, Aster Phoenix was given the last card of the planet series by Principal MacKenzie. Four chapters later, it is revealed that he was given "Jupiter". Though Pluto is no longer considered to be a planet, it was at the time of the manga's initial publication, and thus, the presumed final card in the series is "The Suppression Pluto", used by Atticus.