Zeoticus has the appearance of a middle-aged, handsome looking man with long crimson red hair that is tied in a loose ponytail with a black hairband. He has bright blue eyes just like his two children, Sirzechs and Rias Gremory. He also has a short and red beard or stubble.
Coming from the Gremory Clan that has extraordinary affection, Zeoticus has demonstrated an extremely kind disposition. He is similar to his son Sirzechs in that he is laid back and has a playful side, as he likes dressing up as his clan's mascot "Gomorin" and playing the part. Also like Sirzechs, his antics get him into trouble with his wife Venelana and he becomes frightened when she catches him in the act of fooling around.
Little is known of Zeoticus's past, except that he married Venelana Bael and eventually fathered two children: Sirzechs and Rias. When Sirzechs became the Satan, "Lucifer" and lost his right to become the Head of the Gremory Clan, Zeoticus made an arrangement with the Phenex Clan for his daughter to marry Riser Phenex at some point before the series. At some point, he honed his cooking skills in the human world.
He first appears in Volume 2 at Rias' engagement party and was shocked at the sudden appearance of Issei Hyoudou that is set up by his son. After Issei beats Riser Phenex, he has a conversation with Riser's father, Lord Phenex, apologizing to him and Riser for the results of the match as well as the broken engagement (although Lord Phenex didn't really mind).
In Volume 12, Azazel recalled a conversation that he had with Zeoticus, in which he told Azazel that he sometimes questioned himself as to whether Sirzechs could actually be called a Devil. When asked by Azazel as to what he meant, Zeoticus states the Sirzechs is a mutation of a Devil and that Sirzechs, Ajuka, and another unnamed Devil as the only Super Devils of the Underworld. He also added that perhaps it was Sirzechs and Ajuka's destiny to become Satans because there is no other post for the two of them to have.
In Volume 21, After Issei leaves the hospital with his friends and heads to the battlefield, Zeoticus goes to comfort Issei's parents who are worried about their son, he assures them that they will all return back alive.
In Volume 22, Zeoticus attended Issei's promotion ceremony and when everyone noticed a woman singing the Oppai Dragon song in a opera version Zeoticus was deeply moved by it unlike everyone who was troubled by it, which embarrasses Rias. Zeoticus also attended Rias's graduation ceremony at Kuoh Academy and watched proudly as Rias graduates.
Red Dragon Emperor of the Blazing Truth × White Dragon Emperor of the Morning Star: The True Dragon(s) of the Kuoh AcademyEdit
Zeoticus served as a guest commentator for the Azazel Cup during Issei's Rating Game match with Baraqiel while continuing to embarrass Issei (referring to him as Rias's fiancé).
Powers & AbilitiesEdit
Demonic Powers: As the head of the Gremory, Zeoticus has strong Demonic Power.
Flight: Being a Devil, Zeoticus can fly with his wings.
- Zeoticus's only known peerage member is his Bishop, Heinrich Cornelius Agrippa.
- Zeoticus is likely hundreds of years old, as his Bishop, Heinrich Cornelius Agrippa, lived and died during the early 1500's.
- He acts as the mascot character "Gomorin" to represent the House of Gremory.
- In both the light novel and manga, he and Lord Phenex discuss about the Welsh Dragon and the impending arrival of the Vanishing Dragon, while in the anime this conversation is held between Sirzechs Lucifer and Grayfia Lucifuge.
- In Volume 14, Rias mentions that Zeoticus has a pact with a Magician.
- Venelana reveals that Zeoticus has a harem which she manages.
- Zeoticus is a good cook.
- Zeoticus' name is taken from the characters in the Gundam franchise, Zeon Daikun + Marticus Rex.