When the Overseers arrived in the mortal planes, Lilariah chose three women from the various factions who she felt were pure of heart to ascend: Kali, Lucca, and Xi. These women aided the Overseers in the process of exterminating the Sleepers of Avarrach.
As the Overseers became more involved, they allied themselves with particular figures amongst the mortal factions. For his work in the war against Genesis Industries, Aberion of the Flame Dawn was chosen to ascend. For his work in Reish, Gao Han of the Descendants of the Dragon was likewise chosen to ascend.
At some point, Agent Coyle brieftly joined up with the Overseers. The circumstances surrounding his ascension are unclear.