Anti-Magic Mask

Anti-Magic Mask (抗魔の仮面) refers to a mask first seen to be owned by the Chosen Hero Chronoa. It was given to Shizu to suppress Ifrit, who resided inside her. It was later passed down to Rimuru Tempest upon Shizu's death. Rimuru then gave it to Chloe Aubert as a parting gift after his time as her teacher was over.

While the real mask was left in the hands of Chloe, Rimuru was still able to duplicate a working copy of the mask, though Rimuru modified it to only have the Magic Resistance ability in strengthened form, as its other abilities were useless to him.

During the events of Hero Awakening, it was revealed that Chronoa and Chloe are one and the same, and Chronoa possessed the mask in the past because Chloe brought it back during her time travel. This means the mask is cycled between its users (Chloe/Chronoa -> Shizu -> Rimuru -> Chronoa/Chloe) during these countless time loops. According to Diablo, Rimuru is the source of the mask.

Abilities
The mask is a magic item infused with four effects:
 * Magic Resistance: Dulls any Elemental Magic attacks that the enemies cast while hiding the user's internal magical force.
 * Antidote: Nullifies poison that made contact with the user.
 * Breathing Support: Allows the user to keep their lungs full even if the flames consumed the oxygen around the user.
 * Amplify Senses: Increases the user's senses.

Since the mask is bound by cause and effect, it is indestructible prior to coming into contact with Rimuru. The side effect of this is so great that it could even deflect a direct hit from the Black Primordial, Noir, and even blew off his arm with the force of the recoil.

Noir became obsessed with the mask and had been closely following Shizu's activities ever since their encounter. The reason behind Noir's fascination with Rimuru is because he witnessed the mask crack in his prescense, realizing he was the source of its existence.