Formless (dreamless) implies deathless, so the “end-stage” nocturnal practice is bardo yoga (bardo means “gap, in between, or transitional process”), which is when sleep and dream are used to prepare for death. There is an intimate connection between death and sleep. In Greek mythology, Hypnos (the god of sleep) and Thanatos (the god of death) are not just brothers – they’re twins. In Buddhism, both dream yoga and sleep yoga developed as ways to prepare for death. Once again, bardo yoga transcends but includes all the above tracks.