Xelloss (Japanese: ゼロス Romaji: Zerosu) is a mazoku and the priest of Greater Beast Zelas Metallium in the Slayers series.
Xelloss was created by Zelas during the Kōma War, which took place approximately 1013 years before Slayers TRY. Unlike other subordinates of mazoku lords, Xelloss is the sole immediate servant of Zelas Metallium, and thus a great deal of her power went into his creation. Because of this, Xelloss is the most powerful of all the priests and generals of Ruby Eye Shabranigdu's subordinates.
In the Kōma War, Xelloss singlehandedly killed thousands of golden dragons; he is feared and hated by them ever since. They refer to him as the Dragon Slayer, although he does not like this name, probably because it does not fit the "image" he wants others to view him as. After the war, before serving Hellmaster, Xelloss' duty for a thousand years was to find stray copies of the Claire Bible and destroy them so that humans could not find an easy way to defeat mazoku (with Zanaffar), or utilize the power of the Lord of Nightmares.
Xelloss possesses all the abilities of a high-ranking mazoku, including the ability to teleport with items or even people, and also the ability to maintain an incredibly detailed projected form, mimicking even the insides of the human body. He can also change his human form at will, switching his gender from male to female if he wishes. He has narrow purple eyes that are catlike, and his gaze very cold and sinister. This may very well be intentional: He usually keeps his eyes closed or at least slit, along with wearing a cheerful expression, but when he opens them, his face changes from harmless to menacing in an instant. The clothing he appears to wear and his staff are all part of his physical manifestation and can become as incorporeal as the rest of him. (For example, in the fifth Slayers novel, he was able to slip away from Amelia Wil Tesla Saillune even though she had a tight grip on his clothing.) Before he sold them to Lina, he possessed the Demon's Blood Talismans. He received these during the Kōma War as a reward from Shabranigdu.
Somewhat unusually for a mazoku of his stature, Xelloss' true astral form is that of a simple black cone. When he battles in his true form (which usually occurs when confronting fellow demons), his preferred tactic is to hurtle towards his opponents at high speed like a giant drill, appearing on the physical plane only at the last moment to impale them. As simplistic as this attack may seem, it is powerful enough to kill low-ranking mazoku like Seigram in a single blow, and even seriously damage a general like Rashatt. If the situation warrants it, Xelloss can also divide into a swarm of smaller drills which rapidly skewer a target, repeatedly slipping out of the astral side to attack and then vanishing. While this attack deals less damage per individual hit, the frequency of the hits and the difficulty of dodging makes it all the more effective. It is possible for Xelloss to use this attack while still maintaining his human form.
If there is a debate in Slayers fandom which will never come to an end, it has to be the one about Xelloss' personality. The mystery that surrounds this character leaves many people guessing about what his intentions really are, exactly how loyal he is, and what relationship does he truly have with the other main characters. Opinions vary greatly from the "heartless mazoku" to the "benign trickster". Although these extremities usually ignore some canon facts, less radical members of both sides are able to point out sufficient evidence to support their theory. This is made possible by the fact that Xelloss' actions can be interpreted in numerous ways; what he says is often at odds with what he does, and what he seems to do often appears at odds with the final outcome. Below are some traits which can be stated with a considerable amount of certainty.
Being Greater Beast's servant, Xelloss is her messenger and the medium through which she acts. He never disobeys the direct orders of his superiors, even when he does not actually agree with what they want him to do. Examples of this include when he did not think Valgarv would be swayed to Shabranigdu's side but asked him anyway, and also when Hellmaster Fibrizo borrowed him from his creator in order to protect Lina Inverse so that she would be able to cast the Giga Slave. Evidence suggests, however, that Xelloss likes to and often will exploit whatever small give he has in his orders, in order to fulfill his own desires. This was especially apparent in his assignment with Fibrizo, when he was forced to follow a plan he seemed to dislike entirely.
Xelloss often introduces himself as the Trickster Priest for good reason - he will mislead or cheat in order to get his purpose accomplished, as he himself stated that he never outright lies on principle because his clues usually have at least a fraction of truth in them. Often, he will play pranks just to see the reactions of those around him, or manipulate others to do the work for him seemingly just because he can. His famous catchphrase is "Sore wa himitsu desu" (meaning "That is a secret"). Despite his enormous powers, he prefers subtlety and manipulation over violence, although when Xelloss does enter a battle, he is known to be a ruthless opponent.
Whatever happens, Xelloss always remains polite, referring to everyone, even his enemies, as -san. He also appears to have a certain sense of humor, which shows even in situations where posing as a human is not strictly necessary.
Perhaps Xelloss is the one whose relationship with the rest of the Slayers group differs the most in the novels, compared to the anime. In general it can be said that he is not so integrated into the party in the novels, and the others tolerate him even less. These differences will be noted when necessary regarding each main character.
In the anime, Lina Inverse and Xelloss have a mutual respect for each other at the very least, although it might be a bit of an overstatement to say that they are actually friends. Xelloss seems to enjoy the chaos that follows Lina wherever she goes, and was often seen following her around, even though he had not been instructed to do so. When under orders, Xelloss usually uses Lina's reputation, powers, and personality in order to advance his own agenda, though such often leaves him on the receiving side of a vicious headlock. These traits are more or less present in the novels as well, but to a lesser extent: Xelloss seems to be more distant, perhaps somewhat troubled by the fact that Lina, unlike most other humans he has dealt with, is able to see the larger picture of things and so is not as easily fooled.
Because of his ongoing mission to destroy all of the Clare Bible manuscripts, Xelloss destroyed one such document that Zelgadis Graywords had been in search of, for the sake of a cure; the chimera consequently hates Xelloss with a passion, which does not bother the mazoku the slightest. The idea that Xelloss constantly teases Zelgadiss comes from fanon, however, as after that incident Xelloss never specifically targeted the chimera with his pranks, although the other's enmity proved to be long-lasting.
Xelloss listens to Amelia's "justice speeches" with amusement and mild curiosity, although he is somewhat disturbed by her occasional childish behaviour, especially in the novels. As mazoku are sustained and strengthened by negative human emotions, Amelia has the ability to make Xelloss feel ill, even weak, by bombarding him with long, exuberant rants about the beauty of existence; even her saying "life is wonderful" is enough to make him cringe.
When Xelloss saved her from a group of bandits, Martina Zoana Mel Navratilova became infatuated with him. For his part, Xelloss tolerated her and allowed her to follow him around, amused by her fighting spirit and definitive goals and used her mostly to annoy Lina. Martina eventually dumped Xelloss after finding out that he was a mazoku.
Filia Ul Copt is the only person known to make Xelloss truly angry. Despite his own efforts to be polite, she always puts him down or is rude to him, and thus, he is unpleasant in return. Accustomed to the other dragons' cautious manners when approaching him, Xelloss does not understand from where she got around to blatantly insulting him with names like Namagomi (raw garbage), and he does not quite know whether her attitude comes from courage or just plain stupidity. He never retaliates with anything more than words, though, which is subject to numerous interpretations, along with the slightly noticeable change in their relationship during the second half of Slayers TRY.
Xelloss was sent to Valgarv in order to turn him to Shabranigdu's side. Valgarv refused, and thus Xelloss was ordered to kill him. However, Xelloss underestimated Valgarv's power, and was injured in their fight. Xelloss takes caution around Valgarv, because he might be one of the few who could stand up against him.
Although remaining polite, Xelloss showed little respect when he was confronted by Chaos Dragon Garv, refusing to refer to him with the suffix -sama like he does with the other subordinate lords. The one time that he did call Chaos Dragon -sama, it was in a sarcastic tone of voice. Xelloss showed deep contempt in general towards those who were on Garv's side, such as Valgarv, Kanzel, Mazenda or Seigram.