Faction Paradox mask

Members of Faction Paradox traditionally wore ceremonial masks made of bones. The Book of the War noted that even Cousins not issued with full Faction armour usually carried a mask, if only to wear it at important occasions such as meetings at the Parliament of the Eleven-Day Empire.

Nature
Faction Paradox masks were usually carved out from actual skulls; they were hollowed out but divided into sections, the front section being a detachable faceplate. (PROSE: The Book of the War)

Origins
The original Faction Paradox armour was created entirely from bones from a single source, an "abomination's graveyard" where Homeworlder-Yssgaroth hybrids existed. This source was speculated by The Book of the War to be some kind of parallel universe or alternate timeline where the Yssgaroth won the First War in Heaven against the Great Houses. It was believed to have been discovered, early on in the Faction's history, by Grandfather Paradox and his four principal lieutenants; although depictions of the foundation of House Paradox often depicted the Grandfather already wearing armour, this was likely an anachronistical fabrication. (PROSE: The Book of the War)

Notable Faction members' masks
Justine and Manjuele wore masks made from the bat-like skulls of Time Lords from a history where they lost their war against the Great Vampires. (PROSE: Alien Bodies) These masks resembled Mal'akh skulls, and such skulls were the most common type of Faction Paradox mask. (PROSE: The Book of the War)

However, many members of the Faction wore masks that differed from the mean, and appeared to be from different species than the past-Yssgaroth hybrids. For example, Christèmas' mask was made from a narwhal skull, (PROSE: Weapons Grade Snake Oil) and Cousin Belial was infamous for wearing a mask with mammoth-like features. (PROSE: The Book of the War)

Belle's mask was painted with streaks of blood. (PROSE: Panda and the Airship)

Francesca wore a mask made of synthetic bone. (COMIC: Political Animals)

Godfather Auteur, who had had his skin ripped away from him and was thus a living skeleton held together by shadow, decided to forego a conventional mask, instead letting his shadow-skin peel away around his face to reveal his actual skull. (PROSE: A Bloody (And Public) Domaine)

Father and Mother, the wardens of the Shadow Spire, both wore large bird skulls; Father's was the bleached skull of an Argentavis, "pulled from the mire of extinction", while Mother's was the "weather-beaten" skull of a Haast's eagle. Brother Kifah, meanwhile, wore a jaguar's skull for his mask, and Brother Gustav, a Martian, wore a helmet with a red visor that did not appear to be skull-like at all. (PROSE: Going Once, Going Twice)

In the hands of others
In the late 18th century, one mask fell into the hands of the Service, who kept it in their private collection. The Royal Society frequently requested they be allowed to scientifically examine the mask, but they never got a chance to do before it was lost at the turn of the 19th century. (COMIC: Political Animals)

Representatives of Anonymous wore Faction Paradox skull masks (PROSE: Cobweb and Ivory) as tribute to the hero of Jim Sheldrake's comic The Secret. (PROSE: The Enemy of My Enemy Is My Enemy)

Two masks attached to the identities of by Sibling Same and Sibling Different fell out of a never-was timeline and into the post-Last Great Time War world. Anke Von Grisel put them on display in her Verbier Museum of the Impossible, labelled as having belonged to a "long-forgotten cult"; this allowed Same and Different to claw their way back into reality, although initially as mere immaterial beings. (PROSE: Canaries)