Diodora Astaroth

Diodora Astaroth was the supposed heir of the Astaroth Clan after his older brother Ajuka took the title of Beelzebub. He was one of the main antagonists in Volume 6 of the light novels.

Appearance
He was a gentle-looking, handsome young man with blonde hair as depicted in the novel (Dark Green hair in the anime). Diodora also had a big deep scar on his chest from when he injured himself to have Asia heal it as part of his plan to make her a heretic. He usually wears expensive clothing.

Personality
While initially appearing to be a gentle, well-mannered young man, Diodora was in fact a narcissistic, sinister, vile, and wicked person who would do "whatever it takes" to achieve his desires. He had an utter obsession with nuns and holy-maidens, which was exemplified by the fact that all of his servants were once nuns and maidens that he had acquired after "breaking" them. He enjoyed seeing them with expressions of pain, sadness, and despair which he found to be an ultimate form of entertainment. This prove Diodora to be incredibly sadistic.

He was shown to have a loathing towards Dragons and those connected to them: he once called Issei a "filthy dragon". After being defeated by Issei, he became immensely fearful of him and dragons as well.

History
It was stated by Freed Sellzen that due to his nun fetish, he had preyed on famous nuns and Holy-maidens in various countries around the human world. He would seduce the maidens with his passionate words in order to make them fall in love with him. After the nuns and maidens were cast out by their churches, which was devastating for them, he would appear to save them from the depths of their despair, only to eventually rape them in both body and heart. Diodora would then reincarnate them as his servants who slavishly pledged their loyalty to him.

Sometime prior to the series, Diodora purposely injured himself and appeared before Asia, who healed him. This act of healing a Devil resulted in Asia's eventual excommunication from the Church. He was also present when Raynare stole Asia's Sacred Gear, intending to kill Raynare, save Asia, and then take her as his servant. This plan failed when Issei defeated Raynare and Rias revived Asia.

Birth of the Breast Dragon Emperor
He appeared in Volume 5 as one of the six young Devils at the Young Devil Gathering, Diodora had a Rating Game against Seekvaira Agares where he won (although he was using Ophis' snake during their Rating Game). At the end of the same volume, he reappeared in front of the Gremory group, revealed that he was the Devil that Asia healed years previously and proposed to her.

In Volume 6, Diodora constantly continues to pursue Asia by sending loads of love letters only to avail. He later comes to the Occult Research Club room asking Rias to trade Asia with one of his Bishops but is rejected, Diodora then attempts to flirt with Asia, promising to still obtain her, this action angers Issei as he pulls him away from her. Annoyed at Issei, Diodora calls him "filthy dragon" which causes Asia to slap him, before he leaves, Diodora declares he will defeat Issei in their next Rating Game and win Asia over.

However his scheduled Rating Game against the Gremory Team did not happen after he revealed himself to be an ally of the Khaos Brigade and kidnapped Asia, while leaving his peerage and the Old Satan Faction to handle the Gremory group. When Issei and the rest caught up with Diodora, he revealed he had Asia heal him in the past simply to add her to his collection of nuns. He was defeated by Issei in a one-on-one fight with Issei overpowering him out of anger at what he did to Asia. After his defeat, Shalba Beelzebub appeared. Diodora pleaded with him for aid, only for Shalba to stab him with a weapon of light, and his body dissolved away.

Powers & Abilities
Demonic Powers: Diodora showed some skill in using his demonic powers, able to hurl conjured blades at Issei during their fight.

Trivia

 * Diodora made a brief cameo in chapter 21 of the manga at Rias and Riser's engagement party (he is the figure on the third panel on page 51 of the magazine version in the back).
 * In the English dub of the Highschool DxD BorN, Freed Sellzen called him "Diodora The Explorer". This may be due to his hobbies of exploring various places searching for holy maidens. It may also be a reference to the children's show "Dora the Explorer."