A mask was an object that completely covered someone's face, frequently to conceal identity.
The Units wore masks that connected them as a group mind. Akimus Makassar's mask worked as a processing centre, which meant that he could control the will of anyone in the group mind. (PROSE: The Masks of Makassar)
Voord masks altered the wearers genetic code and turned them into a Voord, provided they were willing to go through with the ritual. The mask became part of the wearer in the process and removing it could lead to disfigurement or more likely dead. (AUDIO: Domain of the Voord)
Señor 105 made masks representing every element on the periodic table. According to some rumours, he gained powers when he wore the masks. (PROSE: Iris Wildthyme y Señor Cientocinco contra Los Monstruos del Fiesta)
Other references Edit
Joy believed that a Silent looked the way it did because it wore a Star Trek mask. (TV: The Impossible Astronaut) Similarly, a hospital porter in Cardiff believed a Weevil's face was a convincing mask. (TV: Everything Changes)