Xix is an Undead who seeks revenge against Nex for the death of Siana. Xix is a candidate for the ceremony on finding out who is the son of the Regis; both Nex and Navarus suspect he is the child of Serin. It is hinted that Siana may be his sister.He is the son of Nex and Serin.
Xix has green eyes and tustled white hair, sometimes shown as brunette in early artwork. Since his fighting style is based on physical attacks, he has a strong warrior build- there are many cuts across his skin from past battles. His skin is slighty tan from traveling. Xix is first shown wearing rogue styled outfits during his revenge escapades. His clothing tends to be loose in nature. Later in the series, he wears clothing given to him by Nex's court-warrior style wear.
Xix is impulsive by nature and easily angered whenever Nex is mentioned. Xix cannot hide his schemes easily since he fails to keep his emotions from showing. He is a justice-seeker, who works to help those who are weaker than him. Whenever he forms a close bond, he does his best to keep that individual safe. Being the sole survivor of his village's massacre, he is remorseful for their deaths. Xix is a vengeful young man whose main goal is growing stronger to avenge the death of Siana, along with the other innocents. He is not the brightest of characters as noted by Just. It takes several attempts of explaining before Xix can understand the whole problem of a whole situation. Ninurrta and Xix share similarity in being easily annoyed. Xix has no problem with beating up his ally Osky whenever he pushes pass Xix's tolerance level.
Xix is searching for Regis Nex, whom he intends to assassinate for the massacre of Banaan Village and his childhood friend Siana. Xix is accompanied by Osky, a demon controller who travels with him throughout the series in the form of a crow. During his search, he mistakes a passing carriage as Nex's and proceeds to try a sneak attack. He is astonished when a woman jumps from the carriage and attempts to duel him; however, Xix proves stronger and takes her hostage. He learns the woman is Princess Yuan, the soon to become fiance of Nex (who gives her up to his son) and is journeying to meet him. When they reach the designated location, Xix tries to hide underneath Yuan to try attacking an unsuspecting Nex. The young man fails to hid his murderous intent and is quickly discovered by Nex. Xix duels the royal guards who fatally wound him, when it is discovered Xix is an undead. Nex lands a final blow by ripping Xix's heart out.
The young man is captured and held prisoner by Nex. While Yuan's wedding ceremony commences, Xix's body is taken over by the demon Skoll-whom was granted to him by Osky. Xix frees himself and crashes the ceremony. In his possessed state, he easily tosses aside the royal guards and proves a challenge to Ninurrta, the crowned prince and believed to be son of Nex. Osky realizing Xix needs his heart to return to normal tries to help the young man. But Skoll destroys Osky and Yuan has to step in and save him. Another young man named Just, a demon who works with Navarus to attain the Regis's throne, appears and easily overpowers Xix, who is given his heart back by Yuan. After returning to normal, Xix flees the castle and runs into a little girl called Miya. The two begin to bond when they are ambushed by two strangers- Night Clan members Seon Yu and One- and Xix learns from them Miya is the Regis's daughter.
The men kidnapped the duo and proceed to take them to a location hiding a fragment of Caladborg's soul and Seon Yu's fiance Rin. Xix is divided between saving Miya from the men or killing her, he chooses the former. While figuring out a way to save Miya, help arrives in the form of Yuan, Owen, and Mala. While the strangers are preoccupied by Yuan and company, he takes Miya down into the dungeon to find her imprisoned teacher. When the group is overpowered by the Night Clan duo, Nex makes his appearance and easily defeats them. However, Xix is knocked aside Nex's attack. A seal located within the dungeon is opened by his blood, from a wound caused by Nex's strike, and a piece of Caladborg's soul is released.
Nex begins to suspect the young man is Serin's son and chooses to take Xix back to the castle for treatment. When he regains consciouness, he is less than thrilled with his predicament of being back in the Merkaba castle. Yuan appears to see how he is doing, she cathces him off guard and he accidently attacks Yuan, who proceeds telling him his location. While questioning Yuan and Miya about the Nex's choice in sparing him, Ninurrta makes an appearance explaining to Xix his blood opened a seal which can only be opened by members of the Regis's bloodline.
A revived Osky takes the group into the past to find answers about who is the true son-before they receive their answer, Ninurrta ruins the memory account by storming off after learning his mother's actions into trying to become queen.
Upon their return to the present, the Regis decides to perform a ceremony where he will learn who is his real son by whoever can release the Imperial Seal. Just passes (through stolen blood, since he is not a true candidate), Ninurrta flees before he is tested, and Nex has to force an unwilling Xix to take the test where he also passes. After releasing the seal, a surprise attack from a Night Clan member, Siana, interuppts the ceremony. Siana kidnaps Ninurrta and begins to attack the Kingdom's defense shield while trying to leave the castle. Xix and his friends catch a glimpse of the girl and prince fleeing, Xix is shocked from seeing his childhood friend.
After their escape, Xix is ordered to travel to Yuan's kingdom to protect the other fragment of Caladborg's soul by Nex. Xix is determined not follow Nex's orders, but Depore-the messager girl since Nex knew his presence would rile the teenager up- pokes fun of Xix's inability to beat the Regis with his limited strength and eventually manages to persuade him into leaving with Yuan.