This beetle-shaped medallion provides three benefits while it is on your person.
Defense
You gain a +1 bonus to Armor Class.
Preservation
The scarab has 12 charges. If you fail a saving throw against a Necromancy spell or a harmful effect originating from an Undead, you can take a Reaction to expend 1 charge and turn the failed save into a successful one. The scarab crumbles into powder and is destroyed when its last charge is expended.
Spell Resistance
You have Advantage on saving throws against spells.