Mask

A mask was an object that completely covered someone's face, frequently to conceal identity.

Uses
The Units wore masks connected as a group mind. Akimus Makassar's mask worked as processing centre, which meant that he could control the will of anyone in the group mind. (PROSE: The Masks of Makassar)

Magnus Greel and Elizabeth X wore masks to hide their appearances. (TV: The Talons of Weng-Chiang, The Beast Below)

Scaroth disguised his various fragments in human form behind masks. (TV: City of Death)

Roboforms wore masks as part of their Santa Claus guises. (TV: The Christmas Invasion, The Runaway Bride)

Some Silurian warriors wore masks. (TV: The Hungry Earth / Cold Blood, et al)

The Soulless wore masks as a representation their belief that Miracle Day had robbed humanity of their souls. (TV: Dead of Night)

Other references
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)

Behind the scenes
The BBC Doctor Who website featured several cut-out masks of aliens from the franchise that could be printed. Masks of varying materials were also available as free gifts in Doctor Who Adventures.