|“||Good day, Sekiryuutei and members of his team. I’m Roygun Belphegor.||”|
Roygun Belphegor is the former Head of the Belphegor Clan, the former second ranker of the Rating Games and a former Ultimate-Class Devil. She reached the top of the Rating Games through her King Piece before being stripped of her rank and all her titles for cheating in the Rating Game due to it. Roygun was also shunned from her household.
Roygun is a beautiful young woman appearing in her twenties with long, wavy, cherry blossom hair and two horns protruding from her head. She wears a high-cut formal dress with high slits and has a well-endowed bust and slim waist.
After becoming a temporary nurse of Kuoh Academy, she wore a white gown and a miniskirt that showed her legs and wears glasses.
Roygun appeared to be a kind and noble woman. Unlike Bedeze, she didn’t have a rebellious side as she tried to stop Bedeze from attacking the Bael clan and take down those who used the King Piece. Roygun became remorseful after she helped the Rating Game’s corruption come into play, yet despite this she didn’t have regrets as she wanted to use the King Piece for fun. Roygun is said to love younger males from their teens to their twenties, as seen when she openly flirted with Issei for having a cute face in front of the female members of his team.
Roygun holds a great deal of love for the Rating Games, even though she used a King Piece to obtain power. Her love for the games were shown when she pledged herself and her servants in front of Issei to be his retainers, to be able to participate in the Azazel Cup, as she can't let go of the Rating Games which she loves so much. She has a pretty laid back personality as even though she was shunned from her household, it just caused her to become inconveniently depressed.
Roygun is shown to be very wise and intelligent as she was able to gain information on Sacred Gears even before Heaven and Grigori made an announcement on them, something that surprises her team leader Issei.
Sometime before the series, Roygun became the Head of the House of Belphegor. At some point, she became the second champion of the Rating Game (unbeknownst to everyone, she was using the King Piece to win).
Powers & Abilities
Immense Demonic Power: Due to the usage of her King piece, Roygun was able to gain immense demonic power that allow her to rise to the top of the Rating Games as the second strongest as a result. Her demonic power was noted to be Satan-Class as she is superior to Bedeze Abaddon, another user of the King Piece, and was second only to Diehauser Belial. She is renowned as one of the strong beauties of the Underworld, along with Grayfia Lucifuge and Serafall Leviathan. In Volume 25, Roygun's power has decreased as she returned the King piece.
- Crack (裂け目, Sakame): As a member of the Belphegor Clan, Roygun has shown incredible mastery in creating a tear on anything. However she is limited against those who are more powerful than her such as Satan and God-class. Using this is what helped make her become the second-ranked Rating Game champion until it was revealed that she used a King Piece. In True Volume 2, Roygun create a technique that expand the damage of her opponents.
- Teleportation: Roygun has demonstrated the ability to teleport herself and others.
- Transformation: Roygun can make her horns disappear when she flickes them.
Immense Stamina: Due to using the King Piece, Roygun had incredible amount of stamina, enabling to help her win the Rating Game matches when she was the second champion. After her King Piece was confiscated, her stamina was depleted greatly but despite that she was able to use her Crack ability three times against Typhon, which earned her Typhon's praise.
Keen Intellect: Roygun has shown to be highly intelligent, as she is capable of gaining information even on the number of Sacred Gears that have increased, as well Heaven and Grigori's research on Sacred Gears. She also gained intel on how Gasper’s Sacred Gear now has a Longinus certification.
Flight: As a pure-blooded Devil, Roygun can fly using her Devil wings.
King Piece (Formerly): Roygun formerly possessed one of the rare pieces known as the King Piece, which were banned by Ajuka Beelzebub due to how dangerous they are. After being exposed of using it by Diehauser Belial, her King piece was confiscated.
- (To Issei): "Sekiryuutei…you have a really cute face. To be honest — I like it."
- (To Issei): "Ufufu, does the Sekiryuutei not like older women?"
- (To Issei): "You sure say some really comforting words. Although I’m not too familiar with the feeling of human ageing, I can still tell that you’re complimenting me."
- (To the members of Team Red Dragon Emperor of the Blazing Truth): "I’ll cheer for you guys. But, no matter what the outcome is, you should enjoy the match, okay?"
- (To Issei): "I will be watching closely to see how far your team can make it to Sekiryuutei — ♪"
- (To Issei): "I, Roygun Belphegor and my peerage have come forward in the hopes of joining under the [Sekiryuutei of Blazing Truth] Hyoudou Issei-sama’s command. At the same time, we implore you to allow us to join the [Sekiryuutei of Blazing Truth] team—"
- (To Issei): "…To put it simply, I wish to stand upon the stage of the Rating Games once more. Although I had past misconduct, if you take the Rating Games away from me, then I…have nothing left. I am a Devil who lives only for the sake of that competition. …But, if I continue the way I am, I cannot return to the Games. …I’m sorry for saying all this because of my own selfishness, but for someone like you who has such reverence and faith in the Underworld, I want to lend you a helping hand."
- (To Issei): "Hyoudou Issei-sama, in exchange, I will dedicate all of myself to you. Even if I have lost the abilities of the [King] piece, the techniques of many good players still remain with me — therefore, can you please consider this seriously?"
- (To Issei and his peerage): "Ufufu. I look forward to seeing how you guys will do in the Pro Rating Game scene."
- (To Issei): "If there’s anything, please come to my place. I’ll look at everything. I can also heal a virginity, you know?"
- In demonology, Belphegor (Lord of the Gap) is a demon and one of the seven princes of Hell, who "helps" people make discoveries. He seduces people by suggesting to them ingenious inventions that will make them rich and tempts people by means of "laziness".
- Belphegor is the chief demon of the deadly sin known as Sloth in Christian tradition.
- Roygun is the first Pure-Blood Devil to have horns from her head.
- Despite the Extra Demons requiring members who wish to participate in the Rating Games to cut ties with their households, Roygun was still able to somehow to become the head of the Belphegor clan.
- Roygun is the second character that wanted to be Issei’s subordinate, the first being Bova Tannin.
- Eventually both Roygun and Bova become members of Team Red Dragon Emperor of the Blazing Truth.
- She has expressed an attraction to Issei and is shown to desire to become his lover, as she needs to find a husband after being disowned by the Belphegor Clan.
- Roygun is a skilled cook and is quite fond of cooking as a hobby.
- Roygun has extensive intelligence network that collects information on her behalf, as she was shown to obtain information before even members of DxD, such as the information of the newly-manifested Longinus. 
- Roygun is one of the two former Rating Game champions who used the King Piece, the other being Bedeze.