|“||I am happy if my Hecate is satisfied.||„|
|~ To Marchosias.|
Sydonay (シュドナイ, Shudonai) is part of Bal Masqué's Trinity and a powerful Crimson Lord. His true name is "Thousand Changes" or "Transformation" (千変 Senpen). In the past, he referred to himself as Chi You (蚩尤, Shiyuu), where he once defeated various Flame Haze from different parts of the world. Later, he returns to his post as part of the Trinity, garnering the title "General" (将軍, Shōgun), and assists the remaining members of the organization in their mission to extract and retrieve the Reiji Maigo, and later, free the Snake of the Festival.
He is voiced by Kenta Miyake in the Japanese version of the anime, while in the English version he is voiced by Eli Gabay in season 1 and Jason Douglas in seasons 2 & 3.
In the past, Kun Wu, which, according to the legend, could cut through jade like paper, and was used to kill Chi You. It is hinted that Di Hong and Chi You (Sydonay) have fought with each other in ancient times. But in the end, contradictory to the factual legend, in the battle at Shanghai's Outlaw branch, Sydonay personally executed Yu Xuan and drove Di Hong back to the Crimson Realm.
While Sydonay acts as a bodyguard for the "Aizen Siblings" as they come to Misaki City. He watches from above as Tiriel and Sydonay looks out the window, commenting to Bel Peol that the place is empty. Bel Peol says that they will make the Seireiden a container for the Reiji Maigo and Hecate, with Hecate agreeing to the plan. Sydonay wants the plan to not put Hecate in danger, with Bel Peol saying that she will become an "eternal existence". Later, the two see a flame, which allows the "Seeking Researcher" Dantalion to contact them. Dantalion tells them that preparations are underway.
Sydonay allows Bel Peol to summon the troops, as there won't be any more fighting. After Bel Peol summons Ribesal, Sydonay notices that he is reluctant to follow the Snake of the Festival's order to enter Xanadu without Pirsoyn, his Jaeger companion. After most of Bal Masqué leave for Xanadu, Sydonay tells Yūji and Bel Peol that he will stay with the former because he made the Leader enjoy himself while fulfilling his ambition. The God of Creation allows this and Sydonay and Yūji watch as he leaves with Bel Peol for Xanadu.
Sydonay and Yūji watch the path to Xanadu when Lamies approaches them. He tells them that he has collected enough Power of Existence and restores his painting, something that was lost to the world. Sydonay is killed by Margery's poem, which was the simultaneous blasts from her heads which were equivalent to the power of over ten thousand Flame Haze's flames (ten million in the anime). Sydonay then appears in a dreamlike afterlife with Hecate, who was surprised he had been killed. He tells her he feels that he wanted to die. They hold hands and walk towards a white light, hoping for the day the Trinity and their leader are together once more.
She says she doesn't know when they will next see each other if she becomes the sacrifice, but he can't hear her. After she is scolded by Bel Peol, Hecate-tan says farewell to Sydonay and disappears. He yells at Bel Peol, before being kicked. Later, Sydonay attends Bel Peol's Naze Nani Shana-tan class. He and the others ridicule François about the form of Grogach's Vessel.
- Sydonay's name is derived from the biblical demon Asmodeus, who is depicted in Collin de Plancy's Dictionnaire Infernal with the features of a chimera-like creature. "Sydonai" or "Sidonay" are among the alternate spellings for Asmodeus.
- Sydonay often fights with Margery Daw ever since they met in New York in the 1930's.
- Sydonay is highly favored by the Snake of the Festival as "he who brings an end to anything that stands in God's way".
- Being a kin of the God of Creation, after being killed by Margery Daw and Shana, he returns to slumber with the other kin, the sacrificed Hecate, until they are needed again when the Crimson Denizens wish to the Snake of the Festival.