The Watchers, meaning "Those Who Watch," "Those Who Are Awake" or "The Ones Who Never Sleep," were a special and mysterious order of angels created by God to observe and report about humanity. They were also created by God to be Earthly shepherds of the first humans.
The Watchers were both physically and spiritually gigantic, at least by the standards of the people who later wrote about them. The Book of Enoch refers to both good and bad Watchers. Those that fell became known as the Grigori (a group whose leaders are Azazel, Samyaza and Satanael) while the rest of the order were implied to be disbanded.
"Origin: Unknown. A monster known as 'one who watches.' It takes the form of a giant eyeball that floats in the air. It is elusive and spies on people for the angels as one of their informants."