Abyssus is the Prince of Macellarius who is highly involved with the Empire of Mu through his work as a civil engineer. He supports numerous rebellion efforts by donating to their causes but his primary focus is his sister, Fate, who is also the Spinner.

Although most people overlook it, he is also a Doll. He was designed as Fate's twin, to provide them with a stronger bond that would help him better suppress the Spinner's spirit. After she was sold to the brothel, he put all his focus on obtaining lucrative secrets for the Organization and to finding a method of helping her escape the brothel.

He shares a deep bond with Hero as well and uses this bond to dampen the effects of miasma poisoning.

It is also known that he has a strong aptitude for elemental skills, particularly darkness, a trait of the Voidsent.