As soon as darthmus died his eternal spirit maximized. He then transformed into this new form. After the death of the toa's leader Dextrix, darthmus took advantage of tis and killed at least five toa with a single blow. But using this energy drained him to the point of suffocation. As this happened the sprit of Detrix emerged from the eternal goldstone. Regenerating Dextrix only had enough energy to conjure his body at a earlier stage in his life. So when he finally regenerated Dextrix was a younger version of himself. The residual energy left from this unfortunately changed most of the life forms around him. Dathmus, dextrix, bespis, and a many other toas were all changed into their younger states. Darthmus no longer holding this power retreated.
About this creation
Oh and credit to the head helmet, not sure who exactly was the first to use it, this was built a while ago!