If the players put on the mask ask them to make a constitution saving throw, DC 13
Success=they will take 3d6 fire Damage
Failure=the mask will fuse to the players face, 3 tries to remove the mask DC 11 DC 13 DC15. will result into 3d6 damage if there are two successes.
When players make an unarmed strike they get to roll 3d6 fire damage as well.