Determined Development

Upon the completed casting of this spell, the jeweled box opens and one creature within range is aged into maturity, if the target is not willing to be aged then they must succeed on a Charisma saving throw. This spell cannot be dispelled by any means short of a greater restoration spell or wish. This spell has no affect on the mental status of the creature and only matures its body not its brain which could cause some harm to the creature if they are not careful. 

The caster can choose whether to have them reach maturity or, if they are still a baby, a juvenile state.