|This article is about a piece of terminology in Umineko no Naku Koro ni.|
In order for a Human to become a witch, another witch must sponsor them as their guardian and recommend them to the Senate. When the recommendation goes through, the Human is bestowed with power from their witch guardian and ascends.
If a witch stops being a guardian, then their pupil will cease to be a witch and transform back into a Human. Lambdadelta is the most prominent guardian in the series, being responsible for Beatrice and EVA-Beatrice's transformations.