Skull helmet
From Tardis Wiki, the free Doctor Who reference
Skull helmets were skull-shaped helmets which were worn by the Sycorax warriors and scribe. (TV: The Christmas Invasion, PROSE: The Final Darkness)
Other references
In 1599, the Tenth Doctor observed that an animal skull reminded him of a Sycorax in the presence of William Shakespeare, inspiring the playwright to use the name. (TV: The Shakespeare Code)