According to Genesis, the fallen angels began their fallen path in the days of
Noah, when they
materialised as human males on
earth. The
nephilim were the
hybrid offspring of the fallen angels and human
females, and they were
huge men with extraordinary
strength who terrorised the people of the time. They were also called
the mighty ones of old, and it is supposed that characters such as
Hercules and whatnot were based on them.
However when the global flood came as described in Genesis chapter 6 they were drowned along with their earthly mothers, and the fallen angels took on their spirit bodies and tried to reclaim their former position in heaven. This God did not allow, and thus they joined the chief rebel angel Satan the devil in opposition to God, and became knows as demons.
The fallen ones became bitter towards God for drowning their children and loved ones and, although their power is severely restricted on earth now, they still have an element of influence over events. Such influence has reportedly been seen in such things as the Necronomicon, the Egyptian book of the dead, which is said to have caused nothing but death and terror in the lives of all those who had a part in translating it.
Fallen angels, or demons, are also known as the ancient ones in the popular Lovecraftian mythos and are said to be desperate to gain access to our realm in order to spread chaos and destruction amongst primitive humanity. Rarr!