Horo was naturally gifted since birth due to his heritage and special circumstances, but adding the gruesome experience of living in silence made him more akin to a monster in a human skin. At the age of 15 he had a body that looked like it was crafted by gods, and stood at the height of 2 meters. He was at the precipice of entering the evolved realm, but before then he wanted to consolidate his foundation by evolving his traits and idol as much as possible because after entering the evolved realm his whole being would evolve automatically and could cause an extreme change in his abilities and spells.
His mother had already set a growth path for his soul idol which is why his core spell was the transmutation spell. He had auxiliary spells like, energy armor, decomposition, illusory grip, link, grant life, and most importantly soul subjugation. All of these spells were extremely unique or personally crafted by his mother. She obtained soul subjugation spell by trading the transmutation spell with a progenitor realm Spell caster, the soul master, and it just so happen to perfectly compliment his lightless eyes, so another illusory connection was made between them.
Horo mainly had to develop his eye trait because for some reason his skeletal trait started its own development since birth as his first two abilities for this trait was present since birth, which were black light and Weightless. During his gruesome training in silence as a little child it awakened the "out of existence" or Non-Existent ability. Due to his bones being practically made out of negative energy so pure and condensed he had a natural passive ability quick heal.
After a lot of development his Lightless Eyes had the abilities chains of the damned, soul snatch, soul subjugation, and lightless realm. Before entering the evolved realm he decided to make one more upgrade that would be extremely compatible with the lightless realm. He used his skills of enchanting he learned over the years from his mothers legacy, spirit naming, his spells transmutation and grant life, and some special materials ; to forge some special creature that resembled , large half meter crows that looked extremely ferocious and had claws sharper then diamonds. With the materials he obtained from missions and the headmaster he was able to forge about thirty of them, and He granted them a unit name Kurai mono tachi, "The Dark Ones". Since they were created by him and used grant life as well as granted them a name they were directly connected to his soul. When he merged them with his Lightless eyes it was a flawless fusion and evolved them again which evolved lightless realm into Realm of the Dark Ones.
When he entered the evolved realm his skeletal trait became immensely more powerful, his bones was twice as thick as before although his body looked no different, they gave off a black light. There was also golden thin engravings all over his skeleton that represented an ability known as karmic tie, his soul module stated that he obtained it from the tree,and he naturally obtained an ability as always with this trait named double impact.
All of his abilities and spells were perfect for the skill set he learned while being honed in silence. He named his battle style Dark Karma Arts. He could see all a description of all of his abilities and personal information on a projected screen that only he can see due to his soul module. This wasn't a special function added by his mother, everyone's had this basic function.
Black light was a passive ability that had defensive as well as offensive features. A barely noticeable black light would appear over Horo's skin for an instance to protect him from any kind of attacks including ethereal, if the attack was not. Strong enough it would be completely damaged, if the attack surpassed the defensive capability of the black light it would absorb most as much of the power and damage that it could l. Whenever Horo attacked physically the black light will automatically appear in the shape of the point of his attack a few inches away and land before the actual attack or land even shen the attack is a little short as well as double the power of his attacks. Most importantly the black light was actually considered part of his body in a literal sense, the black light was him and he was the black light, black light ran off of his physical energy and endurance and the stronger his body the stronger his black light.
Double impact was perfect for black light as they worked in conjunction with each other and made his attacks even more powerful. Whenever his physical blows actually landed it would be three impacts, and the third impact would have quadruple the power of the original attack due to being doubled twice. If only black like landed it would have a double impact still.
Non-Existent made him an unfated one, one who has no destiny in any world, one whose future doesn't exist and can only be carved by his actions.
Weightless gave him the ability to have no body weight if willed and minimized the effect his body had on his surroundings.
Non-existent and weightless evolution paths changed and were slightly conjoined due to an extreme technique, which is ironically Silence. Silence was what was engrained in his very soul through the arduous training that he had to endure his entire childhood at silence. It allowed him to automatically and naturally not make any kind of sound or noise at all times no matter the conditions unless he willed it, it also allowed him to mask his presence to an extreme and with his camouflage techniques it would be hard to visually notice him even if looking at him. With these three working in conjunction it made him the perfect assassin.
Karmic tie was an ability that was much greater than he could ever comprehend as it contained the power of karma which was always a mysterious and basically a myth.
Once he made the link of karma by interacting with a person enough, all his attacks will land regardless of protect or reaction. Why using this ability though it takes massive amount of energy and even life force.