The Ritual of Life is a Nox ceremony in which the power of the mind is used to revive the dead. SG-1 was revived by the Nox after being killed by Apophis. During the ceremony, the Nox are unable to maintain invisibility, but afterwards they are hidden again.
Cross Reference: Anteaus, Lya, Nafrayu, Nox, Ohper, P3X-774
Episode Reference: The Nox