Scarabs are beetles of gold or other metallic colors. They protect people against the effects of other mythical creatures. Most of the 50 or so beetles are in SNAPA custody, and Trackers check them out when going on dangerous missions.
Logan was saved from a basilisk hiss by a scarab. This scarab was originally possessed by SNAPA, then Abigail Hardy stole it and gave to Jackson Wilde, who gave it to Logan. It also allows Logan to see Bob, the deflector who protects the Menagerie.