Unranked Skills were created from the bodies of Warriors and Espers, pertaining to a collection of races, focusing at certain Tiers. The creation of each Unranked Skill required decades to a century of research, expending a tremendous number of bodies of the related races.
Each Unranked Skill used the bodies of a certain number of races as the core, forming the abilities it displayed as the end product. It then used many supplementary materials, all derived from the unique aspects of the bodies of numerous creatures.
The Unranked Skill of the Bone Family, Bone Devour used the bodies of three races to form the core of the Skill: Life Leech, Steel Porcupine, and One-Horned Rhino. The materials used were derived from the bodies of the three races at the Tier 4 level. Many other supplementary materials too were used to harmonise the three cores and create an overall ability.