There are multiple spoilers on this page from current chapters and future, yet untranslated ones so read at your discretion.
The three candidates
Xix became a candidate for the heir legitimacy test when his blood released the seal in Thanatos. The seal is said to be only activated by individuals possessing the Regis' blood. Early on in the story, one of the first hints is a scene showing Xix's heart being pierced by Nex during a confrontation, the scene then changes to show Serin screaming in pain. Another incident hinting towards Xix being Serin's child is when Xix is shown as a newborn being carried into a local village by Serin after she ran away from the palace. Serin leaves the child with the Clan's leader along with Semek. Xix is currently the owner of Semek, the demon stone, which was previously owned by Serin. However,their connection is still uncertain. In later chapters, Just tells Xix that Serin may be his real mother, but is uncertain if Just did this as one of his pranks. In chapter 64 it was revealed that Xix is Serin's son since she called him her son when handing him off to a villager, however it is still uncertain about whether this is true or not. It is also still unknown if his father is the Regis Nex.
- Had no undead qualities prior to receiving Siana's heart.
- Is carrying Siana's heart.
- Later raws reveal his memories of Serin may have belonged to someone else prior to his actual memories of being handed over to the village leader.
- Seon Yu states in future raws that undead are able to take on qualities in their youth so it is uncertain if Xix was previously resurrected by Serin and adapted her traits.
- Serin calls him her son.
- Serin gave him Semek- who allowed him to wield his power temporarily.
- He opened two royal seals.
- He interested Caladbolg who came to pick up Siana.
- Siana, before dying, realizes who Xix is while the reader is left ambiguous.
- Can master some of the same fighting technique Nex uses (though Xix is still on the first stage, while Nex has master 8 out of the 9).
- Nex seems to show more belief that Xix is his son rather than Ninoorut and has actually saved the boy on a few occasions, at one point even preventing Xix from receiving a death blow.
- When he came into contact with a monster contaminated by Caladbolg he remained uninfected (though the level of damage from victim -the monster- contamination is still up for debate).
- In future raws Serin briefly awakens from her eternal slumber to plead with Nex to save "their children". Siana has already been confirmed as their daughter so it's highly probable that Xix is Siana's twin.
- Another raw shows Serin and Nex discussing names for their unborn child and one of the names given is "Xix."
- he has memories of Serin carrying him.
Demon Navarus brought Just before the Regis claiming that he is the Regis's true son. Just is the only candidate confirmed not to be Nex's son since he was created through a contract by Navarus and Osky. Just is the demon Ouroboros, who was created to keep the demon Skoll, inside Xix, in check. He was also able to release the Imperial Seal only after stealing Ninoorut's blood (it is uncertain if the blood used is Ninoorut's). Osky claims that Just needed to acquire the royal blood even before the ceremony was performed. Just antagonizes Ninoorut on his uncertainity of being the Regis's son; but goes on to tell Xix that Serin is possibily his real mother. Just tells Xix straight-forward that he is not the Regis's son, because of his real identity as Ouroboros. Just's actions usually create more questions instead of answers.
- Is a demon creation called Ouroboros that was created to assist Navarus.
- None of his life stories are true since he is using a deceased body as a host.
Ninoorut is the crown prince of Chaos. However, when Demon Navarus brought Just to the palace, Ninoorut began to question if he was really the Regis son. A flashback to the events occurring in the Magnanix shows Ninoorut's mother sleeping with her cousin, Mikhail, during Nex's coronation and asking him to help her become queen in order to seek revenge on the Demon Clan. She goes on to mention her first child would be Mikhail's. After the flashback, Nex held a ceremony with the goal of seeing who could open the seal signaling who was his true son. Ninoorut was kidnapped before being able to complete the ceremony of releasing the Imperial Seal. However, Just was the first candidate to pass the test and the reader is uncertain if it was from the blood he stole from Ninoorut.
- Iffrita slept with Mikhail first and claimed her first child would be his.
- Iffrita is adamant about Ninoorut not performing the Seal Ceremony.
- The moment he became an undead is unclean, making the possibility that he is, in fact, Noche, and thus, this explain why Serin showed that image back then. And Depore saying that she can't explain something, because "everything will be ruined without repair".
- Just uses his blood to open a royal seal secretly.
- Does not become infected when coming into contact with Caladbolg.
- Serin ceases her attack on Ninoorut because she senses he is a member of the Night Clan which Regis Nex is considered part of since he initially came from Earth.
- In future raws after he tears off his horns in grief his appearance changes: his hair turns darker and his facial features start to resemble Serin in some scans. His ears and hair style share similarities to Serin's when her hair is let down.
- Seon Yu claims that Ninoorut is the true son of Serin and Nex that was taken from a fleeing Serin by Iffrita and her father.
- Nex goes berserk when he learns of both Siana and Ninoorut's identity and the revelation is not questioned by him.
- A flashback shows Serin apologizing to a dark-haired infant about being unable to save him, flashing forward, after Ninoorut rips off his horns his hair turns dark briefly.
- Heklaroth's prophecy states the heir will be a child born from Nex and Serin but his son would be lost to him. Nex's cold treatment of Ninoorut throughout the years has turned the prince away so there is truth in Heklaroth's vision as Ninoorut joins the Night Clan- an organization that is Nex's sworn enemy.
- In chapter 123, the Awakening (p.9), after breaking the "horns" and died, it's revealed that Ninnorut is, in fact, an undead, he even showed black hair.