Null-Mask

Before attunement a null-mask looks like a perfectly plain and flat porcelain mask, completely lacking in any features. It seems to weigh a bit less than one would expect from the material and has no visible ways to attack to ones face.
To attune to the mask the use need to hold it firmly to their face for about 2 minutes until the experience a tingling sensation where the mask touches them. At this point one can let go of the mask as it will adhere to ones face and slowly start shaping itself to become a perfect fit. During the process the mask also creates holes for nostrils, mouth and eyes. The whole ordeal takes about 30 minutes, after which the mask rests perfectly against the wearers face.
The mask attaches almost magnetically to the wearers face, following their every facial movement as to become practically unnoticable while worn. Removing the mask requires just a simple tug from the user, or a great show of strength for anyone trying to pry the mask from the face of an unwilling subject.
Wearing the mask focuses the users mind, so that whenever an outside force tries to influence the users mind the mask makes that endeavour much harder.

Nullmask

Adventuring Gear Magical, Mask Common (this item requires attunement) [Abjuration]

A plain mask seemingly made out of porcelain. When attuned, the mask takes the shape of the bearers face and the user may spend a bonus action any time they wish to don the mask.
If attuned and worn the mask grants the user advantage on all rolls to resist being Charmed or Frightened.

Cost: 300gp