Scarab of Protection
Wondrous Item, legendary, requires attunement · 2024 rules, SRD 5.2
This beetle-shaped medallion provides three bene-fits 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, youcan 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.
Also in the 2014 rules (SRD 5.1).