Dream Oneiros

Dream God Oneiros (夢神オネイロス, Mushin Oneirosu) is the leader of the gods of dreams.

He does not exist in Greek mythology, where oneiroi is the term for "dreams". Colloquially, the term refers to Morpheus, Phantasos and Phobetor.

Manga
Oneiros is sent with his ​​three brothers in search of Pegasus Tenma, with orders to imprison Pegasus Tenma body and soul in the World of Dream where are trapped the souls of heroes and kings. After doing so without the slightest difficulty, his brother Modeler Morpheus locks Tenma in World Of Dream, and retires to Mundso Oneiros of Dreams. After the defeats of Morpheus, Portrayer Phantasos and Vision Icelus, Oneiros is presented to the winners, Pegasus Tenma and Capricorn El Cid , who explains that the gods exist in a dimension that humans cannot understand, and still rely on their souls, after which they are fused with Oneiros, resulting in a similar creature to a Centaur. Tenma and El Cid attack the god, but he seems immune totheir attacks, and decides to destroy them once and for all with his technique Guardian's Oracle, but the Saints are protected by Athena, which has just reached Morphia to rescue the soul of Sagittarius Sisyphos. To protect Athena from Oneiros possible attacks, El Cid cut the space of the Dreams World to create a connection to the real world, and with the help of Tenma, Oneiros is push through the fissure. Once in the real world, Oneiros discover three subordinates of El Cid who had come to the scene to help his master, and kills them with one blow. Tenma and El Cid, helped by Unicorn Yato and Crane Yuzuriha, who have just arrived, continue to attack the god, but it survives even after being cut into four parts by the Gold Saints. But then Sagittarius Sisyphus, that has returned to the Sanctuary by Athena, shoot from there the Golden Arrow of Sagittarius, imbued with the Cosmo of the goddess. When El Cid sees the arrival of the arrow, he cut the arrow into four with his sharp technique, and each cut arrow attacks every one of the four souls of the gods that make up the body of Oneiros. Before dying, Oneiros tries to kill Tenma, but is prevented by El Cid by stabbing his hand in his chest, after which both perish in a huge explosion.

Anime
His story is identical, including some extra scenes in which Hypnos calls Oneiros and the other gods to inform them of their mission. Besides he can summon his fallen brother souls and united with them the Guardian's Oracle.

Techniques
Guardian's Oracle :  (ガーディアンズ·オラクル, Oracle of the Guardians): Oneiros, fused with his three brothers, is able to trigger this attack which causes a big explosion around. The energy released by the blast can even destroy souls, thus preventing, according to Oneiros, any reincarnation.

Habrilidades
Fusion : Oneiros summons the souls of his brothers and collects them into their body. His appearance changes, their Surplice takes a form similar to a centaur. The upper body remains that of Oneiros, but now sporting two pairs of extra arms

Trivia

 * Oneiros means "dreams" in Greek.
 * It is unknown whether Oneiros can use the Guardian's Oracle by himself, or if he need to merge before with the other gods of Dreams.
 * It is curious that Shiori Teshirogi create a god of dreams that is not present in Greek mythology, giving the generic name are the gods of dreams. The fact that Oneiros can merge with the other three gods, creating a single being, is a clear reference to this fact.
 * Apparently El Cid Oneiros destroys the soul and those of their brethren with the Golden Arrow shoot by Sisyphus and Athena, completely destroying them, a way by The Author to explain why these gods did not appear in the battle of the twentieth century.