Simbad Blue and Gold Skull Shackle
The skull is considered to be the throne of the life force of the body and of the spirit. Hence the desire of many cultures to preserve for themselves the skulls of the dead, in the belief that this act will give them the spiritual power that their holders had in life. In the general sense, it is also the emblem of the expiration of existence, which appears in literary examples like Hamlet or Faust. Being the remainder of the living being once dead, like a snail shell, Acquires the sense of glass of life and thought. Hence the use of skulls as a receptacle for life at its highest level by the alchemists in their transmutation operations.