Scarab of Protection

After being held in your hand for 1 round, this scarab medallion shimmers with magical inscriptions. The scarab has 12 charges, crumbling into dust when it has no charges left. This item has two benefits while it is on your person. First, you gain _advantage_ on _saving throws_ made against spells. Second, if you fail a saving throw against a necromancy spell or either an attack from or trait of an undead creature, you may instead succeed on the saving throw by using your reaction to expend a charge from the scarab.