A Contest of Nisse and Release
Defeated in the Primordial War, the Yozis are the Primordials that are now imprisoned in (and comprise) Hell. Together with their destroyed brothers, the Neverborn they have since schemed against the gods and exalted by breaking open the Jade Prison and stealing the imprisoned Exaltations.
Upon losing the Primordial War, those Primordials that became the Yozis were forever changed. They had their structure altered by the terms of their imprisonment to such degree that they lost their integral souls, which allowed them, for example, to alter existing Exalts and twisting them to their own designs.