The ritual of Quenching the Lambent Flame was developed by the Wanderer, Mictlantecuhtli, after learning the basics from the Maya priests. It raises a Vampire's generation to 13th, effectively making her weaker but able to sustain herself better with the blood of animals.
The ritual takes an hour during which the subject must be motionless or immobilized in the center of a circle drawn with his own blood. If the subject is willing then no roll is necessary, otherwise the caster must roll Intelligence + Thaumaturgy with a difficulty equal to the subjects Willpower.
Snippets of this ritual have made their way into Kindred society through the Codex of the Damned.