Arch has long blonde hair which he ties in two tails and has light green eyes, and, as an Elf, he has pointy ears. He wears white and purple clothes with purple lines similar to Fortuna and Emilia's own.
Arch was absolutely loyal towards his superior, Fortuna. In addition to that, he was friendly towards Emilia as he claimed it wasn't her fault for the attack when she blamed herself.
Arch was an elf living within the Great Elior Forest who, along with his fellow forest dwellers, protected a mysterious seal and a half-elf child named Emilia who could unlock it. Despite his youth, Arch was a strong warrior proficient in magic who was slated to become the Guardian of Emilia once the elven woman Fortuna retired. A kind young man, Arch cared deeply for Emilia and her surrogate mother Fortuna.
Unfortunately, a radical element of Witch Cult led by the Sin Archbishop of Greed Regulus Corneas and the Witch of Vainglory Pandora attacked the elven settlement in an attempt to seize Emilia and unlock the mysterious seal. Emilia was entrusted to Arch by Fortuna who named him the new Guardian and instructed him to flee the forest with the child. Although apprehensive, Arch agreed and made for the exit.
However, his life was cut short when the plague-bringing Demon beast known as the Kurohebi intercepted the pair as they tried to escape. stayed behind and valiantly sacrificed himself so that Emilia could escape the forest and live happily. His kindness and strength of will earned him a permanent place in Emilia's heart as she remembered him later in her life.
Magic User (魔法使い Maho Tsukai): Elior was capable of using magic. Although most people specialized in only one of the six magical elements, Arch could conjure spells from at least two different elements—water and wind. The water element related to life and the rejuvenation of wounds and the wind element focused on directing external power rather than power found within a person's body.
- Huma (ヒューマ): Using water magic, Arch had the capability to rapidly cool the air around him to the point that he could conjure ice out of thin air. The most simple variant of this technique, which Arch could use, was called "Huma." The future Guardian exhibited use of Huma when he cauterized his own leg with a block of ice after he sliced it off with wind magic to stop the venom Kurohebi.
- In a Q&A, the author stated that the possibility of Arch reappearing in the story was a spoiler.