you'll reveal a hidden path that takes to a chest where the Silver Scarab is. Here's a tip to find the invisible floor; start throwing knives or Kukris to the zone below when you reach the middle ...

The Incantation Scarab is a Helm in Elden Ring. This item doesn't belong to any Armor Set. Golden scarab worn directly on the head. These scarabs roll clumps of incantations during their labors.