Amulet of perpetual youth

The Brooch of Perpetual Youth is quite simply a talisman that is worn that makes the wearer appear to be young and have a youthful appearance, similar to a Phylactery of long years  In Human years an age that can be relatively related to wearing a brooch would be 28 years old. In other races the exact age can vary. One well known wearer of such a Brooch is Gromph Baenre Archmage of Menzoberranzan. The Brooch is obviously magical, yet has mysterious properties. One such property is that the magic of the brooch can in no way be canceled or dispelled. Gromph has frequently erected Anti-magic shells around himself yet continued to remain young via the magic of the Brooch. Also the Brooch will have no effect on a child of any race if worn. The magic somehow attunes itself to whatever race wears it and the magic will not take effect unless it senses that the wearer is above a certain age... obviously much more study is required to understand the full characteristics of the Brooch of Perpetual Youth.