During this event the young people of the tribe are honored and given their title, and the profession they will have for the rest of their life. Every member of their society who is at least 15 partake in the event. Given that the Heavens Sunder only happens every three years, there can be a huge age gap between the initiates. The ones who are 15 on the day of their symbiosis are seen as particularly blessed.
After the ceremony, all the initiates go and partake in a massive orgy with the hope of creating the next generation of people for the tribe. This way, children conceived on this night, will not know who their father is, which helps foster the community outlook of the tribe.