The Haunted Mask is an evil, living entity and antagonist in the Goosebumps series.
The Haunted Mask
Long ago, there was a man who hated the way he looked after being in an accident, considering himself ugly. The man used magic to try and create face like masks to hide his deformity, but because of his self-loathing, the masks became hideous and evil, the worst being a green skinned fanged one, dubbed the Haunted Mask. When the man got the hint, he finally accepted what he was, and finally created a mask that stayed the way it was made.
But the Haunted Mask waited until it could find a suitable host; enter Carly Beth Caldwell, a girl who hated the way she was. The Mask slowly possessd the poor girl, until it wouldn't come off and was becoming her face. The Mask Maker told Carly that the only way to rid herself of it was a symbol of love, that being a mold of her by her mother. Free of the Mask, Carly Beth buried it in a cemetery.
The Haunted Mask II
In the television adaptation, the Mask returns to life one year later and forces itself onto its creator. With its new body, the Mask lures Carly Beth's classmate Steve to the store where oter masks were kept. Steve chose one that resembled an old man. The old man mask fused to Steve's face and made him physically weak. The Mask used Steve as its minion, ordering him to bring it the sculptured head of Carly Beth and destroy it, so that the Mask would be able to possess her once again. Carly Beth confronts the mask, but evades it at the stroke of midnight, at which point the Mask goes dormant. The Mask's creator reveals that the power of the masks is only effective on Halloween. Carly Beth and Steve then burn their masks and announce their retirement from trick or treating. The Mask briefly comes back to life, only to be mauled by Steve's dog and buried. Presumably the Mask would just wait for the next Halloween before coming back to life and possessing a new host.