Gemini Defteros (双子座のデフテロス Jemini no Defuterosu?), also known as the "Demon of Kanon Island" (カノン島の鬼 Kanon-tō no Oni?) and addressed by Asmita's ghost as "a man who can destroy the stars of a galaxy", first reveals himself as a man of incredible savagery, although he is at heart a serene warrior. He lives by the philosophy of survival of the strongest. Twin brother of the late Gemini Aspros. Defteros' name, alternatively spelled as Jemini no Defuterosu (双子座の二番目?), meaning "Second one", reveals his condition as the younger of the twins. During his younger years, Defteros suffered the rejection of Sanctuary as a Saint apprentice. Forced to wear an iron mask to hide his existence from the outer world, Defteros was protected by his older brother Aspros, who was considered the rightful future heir of the Gemini Gold Cloth.. In Kanon Island, Defteros helps Tenma to reach briefly the 7th Sense and to understand how to combine the mastery of Cosmo in order to become one with nature as well. After training the young Saint, Defteros leaves telling an unconscious Tenma to take good care of the Pegasus Cloth, possibly out of respect for Asmita whose blood restored it. Later on, he is seen healing Libra Dohko's wound caused by Hades' sword by using Athena's blood. He then asks him to carry a flask of the same blood to Athena's statue in Sanctuary, and reveals to him his true identity as the Gemini Gold Saint. He reveals to Dohko that his life was saved by Bennu Kagaho, by bringing him to Kanon Island. He enters the war against Hades in Sanctuary, surprising Bennu Kagaho to save Dohko's life by means of opening an alternate dimension with his Another Dimension (アナザーディメンション Anazā Dimenshon?) attack. He tells Kagaho to convey a message to Hades, that they're arriving to the Lost Canvas and that his defeat is near. He later removes the secret of Athena's Cloth from Dohko's memory and sends him with it to the Lost Canvas. ~!Remaining within the vacuum of the Another Dimension, Defteros is challenged by his brother Aspros, who was revived by Hades in exchange of his loyalty and the secret of Athena's Cloth. Later, they resume their encounter in the 4th Demon Temple: Mars, which now resembles the Temple of the Twins in Sanctuary. Both warriors engage each other in battle while reminiscing about their past. It was revealed that Defteros was manipulated in order to assassinate the Pope by his older brother, Aspros, with the attack Demon Emperor Fist, a technique that grants the user complete control of the target until the victim has witnessed the death of someone. Defteros was able to fight off the effects of the technique with help of Virgo Asmita long enough to deliver a fatal blow to his brother, completely freeing himself. After his defeat, Aspros applies the Delusional Fist on himself before dying. Defteros took Aspros' body with him and the Gemini Gold Cloth to Kanon Island. Returning to the battle at the Mars Temple, Defteros is put under the control of Aspros again. To counter the attack, Defteros exhibits a newly introduced technique, the Mavros Eruption Clast (マブロスエラプションクラスト Maburosu Erapushon Kurasuto?), (from the Ancient Greek μαύρος, "black") with which Defteros summons magma from the depths of earth to create a violent explosion. Defteros reveals to Aspros that he surpassed his own limits during his training at Kanon Island and uses his technique to free himself again from his brother's control. Even so, Aspros counters the technique easily with his Galaxian Explosion, overpowering the Gemini Saint into submission. Putting aside fond memories and respect for the once-gentle brother he knew, Defteros engages Aspros in a final effort, pitting his own Galaxian Explosion against his brother's, out of which only one will come as survivor and final victor. Seizing the moment of the clash of the Explosions, Defteros hits his brother with a technique that sacrifices his own life, nullifying the effects of the Delusional Fist on Aspros, making him return to his senses. Afterward, Defteros' body vaporizes, leaving behind the Gemini Gold Cloth. Having sacrificed his life in order to restore his brother's sanity, Defteros remained content in merging his soul with his brother's..
