Ageless

The purpose of this cantrip is as the name implies, you stop aging, or more precisely, you stay the age you were when the spell was cast. This spell does not make you immortal, or effect your healing. You can still die like any mortal. Though you are immune to any effects that would cause you to age or become younger. 

Once this spell is cast it can only be broken by the caster, by the gods, or by a wish spell. 

This cantrip is one that was kept secret, and only passed down to those worthy,  Shrouded in mystery, the details of how this are unknown.