Vessels for Apeiron's Essence (EAs)

The Vessels for Apeiron's Essence were a family bloodline that Apeiron had engineered through Sith Sorcery and Sith Alchemy to have a specific genetic design, eventually giving birth every two generations a youth that was a physical and genetic replica of his first Vessel whom he had also created, it allowed Apeiron to have an infinite number of bodies every two generations in which Apeiron could transfer his essence into and continue the cycle eternally.

This continued from long before 5100 BBY to 5000 BBY, when years of research and the gaining of his final body allowed Apeiron's plans to come to fruition when Apeiron gained type of Immortality for himself, in the form of a powerful Sith Alchemical spell that allowed his final Vessel to become eternally young and immune to illness, disease and Dark side corruption.

It was revealed later however, that the unnamed family line did not die out after they were no-longer useful but instead were made servants of their unknowing benefactor even after he came "immortal", whenever a new Doppelganger was born he took the youth on as his apprentice and used him as his eyes and ears everywhere although he didn't know it. The mental link was also a back-up plan, should his "immortal body" be killed in combat, he could transfer his spirit along the mental link and take his Doppelgangers body for himself as a backup plan where he would then repeat the Ritual of Invigoration.