The Amulet of Daylight was an ancient and powerful artifact from the Tales of Arcadia franchise. The Amulet was created by Merlin and his apprentice Douxie Casperan and used by Trollhunters, which was used to store their armor and the Sword of Daylight. It is summoned with the chant, "For the glory of Merlin, Daylight is mine to command!"
Usually, the Amulet can only be activated by the Trollhunter so it is not operational if it falls in the wrong hands, acting as a fail safe. The amulet was later destroyed by the Arcane Order so they could bring back Morgana to life.