Lye is described as being short; as tall as Rem, if not even shorter.He has long, light-brown hair that goes down to his knees, the tips of which are smeared with blood and dirt. His most distinctive facial features are his emerald green eyes and teeth shaped as numerous sharp fangs. Under his unkempt hair, he's usually wearing tattered blue and purple striped clothes covered in dirt, grime and large amounts of blood splatter, and a standard, also tattered, dirty and bloodied Witch Cult robe. On his filthy and soiled hands, Lye strapped two Witch Cult daggers which he uses as his means of attacking and defending.
In Arc 5, Lye fully shows off his body, revealing a multitude of grotesque and horrid wounds, ranging from whip marks to bite and scratch marks. He gives off an unnatural and bizarre aura; completely opposite from what you would expect from a 13 year old child.
Personality
Lye believes that everything comes down to experiences, and the one who manages to get better knowledge is the one who enriches his life and wins over people, also remarking that knowledge is power and memories are bonds, ultimately concluding that this means that he is the greatest. Due to that, he also refers to himself as intellectual Sin Archbishop.
Unlike Roy, Lye also strongly believes that if the number of lives in the world is limited, then the amount of worthy food is limited, and will hence not miss a single chance of eating them. Lye remarks how Subaru is his "savior", as he is able to remember the people who have gotten their names eaten, pointing out how the forgotten feelings of rage and revenge were a source of dissatisfaction, but Subaru was an exception to this. Lye also seems to look out for Louis, pointing out how she may be happy if he was to eat Otto, Felt and Dynas.
Lye's fighting style is vastly different from his brother's, often giving his opponents a chance to "prove" themselves as being worthy of being his meal and likes to compete with them, before ultimately eating them and claiming their abilities for himself through Authority of Gluttony.
He strongly resents merchants, referring to them as "people who place prices on things and sell them to line their own pockets. They're dead people who place the values and opinions of people on a scale before calculating". Lye cares about the quality of the lives he eats, and frequently remarks on how he is not like Roy and won't be satisfied by eating just anything.
Also, the three speak in a collective manner using us and we instead of first or third person.
Abilities
Authority of Gluttony (暴食の権能 Bōshoku no Ken'nō): Lye is able to use the Authority of Gluttony.
Gluttony (暴食 Bōshoku)
Lye can eat the name and memories of their opponent. To eat a name, he touches them with his left hand, then licks the palm of the same hand. Things such as experience, talent, and the likes and dislikes of human relationships serve as food for him, allowing him to take advantage of any abilities or memories his opponents had. However, if he eats a fake name, he becomes plagued with severe nausea.
Those that have had their names eaten have their existences erased from the world, destroying any human relationships along with negating any contracts with Spirits.
Those that have their memories eaten become amnesic and any characteristics they may have had are reset, effectively making them into a different person.
Those that have both their name and memories eaten simply become a shell, and although they live, they no longer eat, excrete waste, or age, putting them in suspended animation.
They cannot eat the same person twice until that individual gains enough new memories to establish a different sense of self from their old one.
Eclipse (蝕)
Eclipse is considered to be the trump card of gluttony and it also has two types; Solar Eclipse (日食 Nisshoku) and Lunar Eclipse (月食 Gesshoku).
Lunar Eclipse allows the holder to use the victims' memories and harvest their skills and knowledge. Lye used Lunar Eclipse to boost his physical strength and perform numerous martial art techniques including The Palm of the Fist King and the Leaper technique. It is worth noting that by eating a person's name and using Lunar Eclipse, Lye does not gain his victims' Divine Protections, Spirit Arts or Authorities.
Solar Eclipse, however, allows the holder to harvest his victims' name and transform their appearance accordingly. Louis, for example, transformed into Neiji Rockheart and numerous other victims she and her two brothers had eaten throughout the years using her sibling's body.
Master Class Fighter: Through the accumulation of souls eaten, Lye gains any abilities his victims once had such as martial art techniques and magic. In turn, this has granted him extraordinary combat strength. He is able to overpower multiple strong opponents at once, as shown in Arc 6.
Huma (ヒューマ): Lye creates a shining water barrier that blocks other projectiles and sorts of magic. However, if the incoming magic is stronger than the shield it will get through it and cause damage to the user.
El Huma (エル・ヒューマ): Lye forms and shoots multitudes of ice spikes from their hands which easily pierce through human flesh that immediately vanish on impact.
Palm of the Fist King: An powerful strike that ruptures a person's internal organs, as well as outright, destroys physical objects like swords. It can also bypass mana based defensive techniques. The move originally belonged to Neiji Rockheart.
Leaper technique: This technique allows Lye to move with extreme speed undetectable by the naked eye, essentially allowing him to leap behind his opponents or avoid extremely precise and quick attacks. Due to the extreme speed, it seems like he's teleporting around the battlefield. He's also capable of utilizing it vertically, making it appear as if he's flying. This move originally belonged to Dorkell.
Ice Brand Arts (アイスブランドアーツ): Whenever Lye successfully ate Emilia's "name", he copied her Ice Brand Arts with the help of his Lunar Eclipse. This technique allows Lye to instantly conjure ice made weapons which he can use and freely manipulate in close-quarters combat. The weapons are very sturdy and are even capable of withstanding heat.
Because Lye, Roy and Louis possess the Witch Factors of Gluttony which were previously in Daphne's possession, they can direct Demon Beasts to attack certain areas. This is why the White Whale’s attacks were coordinated with those of the Witch Cult. In Arc 6, Lye and Roy are able to get to the Pleiades Watchtower in half a day by commanding the Demon Beasts in the Augria Sand Dunes, and order them to attack the Watchtower.
Equipment: Lye skillfully uses two standard Witch Cult daggers that are wrapped around on his arms.
Trivia
Lye's last name is also the traditional name for the star Zeta Ceti, which is apart of the constellation Cetus.
He is "Gourmet" for his obsession with preparation before a meal.
Solar Eclipse also changes their "gate" to that of the current eaten victim being in use. This is how Lye was able to avoid the blast from Echidna's Meteor Staff.
Lye dislikes using Solar Eclipse. According to him, it makes him experience the victims' thoughts which make him feel like he's being damaged. He described the feeling as unbearable.
In episode 26, Lye can be seen using the Leaper technique to avoid Rem's ice spears.
in the novels, he was first seen using this technique in arc 5.
