Thanatos, the god who rules over death (死を司る神タナトス - shi wo kami tsukasadoru tanatosu) is a god in the service of Hades
Holy War XVI Century
The Sanctuary , Athena won the holy war by defeating Hades with the help of Saints survivors. The twin gods then appear and kill the Athena Saints. Only Cancer Sage and the Altar Hakurei are alive thanks to the protection of the sword of Athena.
Thanatos and Hypnos attack Athena and said they are preparing for holy war in the next two centuries. Thanatos opens the Hyperdimension and plunges with his brother. Athena off to meet them asking Hakurei and Sage to stay alive.Saints maintain both a real hatred against the twin gods who took the lives of their comrades.
Holy War XVIII Century (Lost Canvas Era)
The two brothers
Hypnos and Thanatos appear to Pandora at the Cathedral of Hades. They are worried: Alone seems always present in the body of the god of the underworld. They urge Pandora act. This will send assassins to kill Pegasus Tenma held responsible. But the killers fail in their mission.
The twin gods returned to the charge. They want to shut Hades in a special workshop to remove the disturbing elements and it focuses on the realization of Lost Canvas . After Pandora has succeeded in its mission, Thanatos and Hypnos begin a song and around the cathedral a double barrier while Tenma , Yato and Yuzuriha head to this place.
Thanatos gave powers to the Nasu Veronica to protect the forest of death (including giving him an immortal body) while he and his brother are flying in the palace of the gods twins. When Veronica is about to get beat by Manigoldo in Yomotsu Hirasaka , God orders the specters at least take the Gold Saint with him in death. Veronica fails again, Manigoldo happens to track the god with the trace left by the god cosmos. Manigoldo interrupts chess twins and said he wanted to face the god of death himself!
Against the teacher and the student
Thanatos blocks Manigoldo punch with one chess piece. Hypnos decides to leave the palace. The god of death plays with the pieces that come to life and attack the Gold Saint. It get rid of them with the Shiki Kisōen Seki and attack towards the god. Thanatos dons his Surplice and invokes Hyperdimension . But Sage comes out and defeated the dimension.
Sage said he planned events. By following Tenma by Manigoldo he doubted he would meet the god of death. Thanatos does not care and starts Tartaros Phobia , the souls of dead attacking the teacher and the student. The Gold Saint uses Shiki Konso Seki Ha makes them explode. Manigoldo mocks the god who responds by saying that mortals are not even worthy to be noticed.
The god launches Terrible Providence blank at the Saint that emerges badly wounded. Manigoldo comes out through the seals Athena possessed Sage. It throws them against his opponent. But they are insufficient, the Thanatos breath and destroyed a large part of the palace air.
Manigoldo it carries a punch in the face. God, enraged, extends Hyperdimension. The Gold Saint has a leg torn off. Sage tries to use the Shiki Seki Meikai Ha to eradicate the soul of the god's human receptacle. But the spirit of Thanatos is powerful. The Gold Saint wakes up and does the same attack to help his master. After a moment, he grabs the human body and throws him in Hyperdimension. He sprayed with him.
Thanatos does not take it. He decides to take possession of the body of Sage. Thus, it can go to the Sanctuary and kill Athena easily. However, it quickly became disillusioned because Sage has taken the Cloth of the altar of his brother. Hakurei and he stored energy for centuries in the box in the Cloth. Thanatos attacks the body from the inside but it does not stand confinement.