Spire

Spire is a natural born Crepus citizen, and even from first appearance is obviously a ninja.

Season 2
At age 16, Spire is first seen in black garb, with short silver hair, with a single long braid of hair extending off of the back of his head. Referred to as 'The worst Ninja' his mannerisms are clunky and not what you would expect from a trained ninja. Curiously his weapons; "Spike" and "Jet", Are twin curved swords, that are connected by an ethereal chain that links the weapons together, but passes harmlessly through objects. This chain has been known to extend to reasonably far distances. Not unlike that of a 'hookshot'. As season 2 progressed, Spires abilities notably improve as the series continues. Spire has a companion known as 'Mog', a tiny sized white bear with imp wings and a pom-pom on its head. Mog offers advice to Spire in a language unknown to the audience throughout the season.

Season 3
During the transition between seasons 2 and 3, Mog is lost during the transportation between worlds. Spires abilities continue to improve. Perhaps even surpassing his other family members at this point. Spire most notably unleashes an incredibly powerful ability during the tournaments events "ABILITY NAME" allowed him to dash between shadows that he created himself to strike multiple times in several different places.

Background
The most notable aspect of Spire isn't Spire himself, it's his family. Spire is from a family of 8 children, his other siblings are all girls, and are all concerted (in season 2 at least) to be better ninjas than him. During his first appearance he is living with one of his sisters when he meets the other characters, and throughout Season 2, many more of his sisters show up in the story. It is unknown what has happened to Spires parents, as the series does not go into detail with them.

Spire's lifelong companion, Mog, constantly has helped him with his life as a whole. Trying to build his confidence for the entirety of Season 2, after the transition to the modern world, is it theorized that the girl in the white dress who goes by Dawn is Mog's true identity."Order of Shadows"