Vile Extension (Evil)
This spell is one of the evilest spells in creation, and also one of the most useful. By means of casting this spell, you can actually permanently alter what your actual age is.
The Netbook of Witches and Warlocks
By Timothy S. Brannan and The Netbook of Witches and Warlocks Team
Level: Witch 9
Components: V S M
Casting Time: 1 full hour
Target, Effect, Area: Self
Duration: See below
Casting Vile Extension requires a ritualistic sacrifice of a virgin of the same sex as yourself, which takes place at the end of the spells casting time. Upon completion of casting the spell, the caster takes the same age as the target sacrificed. The normal penalties that the caster might incur for being of a particular age are negated, provided that the target was young enough for such bonuses. You still retain bonuses to mental ability traits.
The material component is a live humanoid that has already been through puberty, and an athame.