In Egyptian history, the snake occupies a primary role with the Nile cobra adorning the crown of the pharaoh in ancient times. It was worshipped as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide (Cleopatra). The ouroboros was a well-known ancient Egyptian symbol of a serpent swallowing its own tail. The precursor to the ouroboros was the "Many-Faced", a serpent with five heads, who, according to the Amduat, the oldest surviving Book of the Afterlife, was said to coil around the corpse of the sun god Ra protectively. The earliest surviving depiction of a "true" ouroboros comes from the gilded shrines in the tomb of Tutankhamun. In the early centuries AD, the ouroboros was adopted as a symbol by Gnostic Christians and chapter 136 of the "Pistis Sophia", an early Gnostic text, describes "a great dragon whose tail is in its mouth". In medieval alchemy, the ouroboros became a typical western dragon with wings, legs, and a tail.