Lilith as the Mother of the Nephilim Giants
In the Jewish Apocrypha, Lilith is a Mesopotamian demon who was created by God to be Adam's first wife. Lilith disobeyed Adam's commands and so was rejected by Adam. After that, she was cast out of the Garden of Eden. In retribution, she became a demon and promised to give birth to a race of demons named "Lilim" who would murder humanity's children. From "Lilith's Cave," Lilith's Cave: Jewish tales of the supernatural
The "Lilim" are the Neph "ilim" whose gigantic skeletal remains have been found extensively in the British Isles and the Ohio Valley within the burial mounds. In Genesis 6: 4 it says that the giant race was spawned by the union of the Fallen Angels and mortal women. "There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown."
The Apocrypha corroborates the version that attributes Lillith as the mother of the Nephilim. "Though he avoided intercourse with Eve, Adam was visited in his sleep by female spirits, and from his union with them sprang shades and demons of various kinds, and they were endowed with peculiar gifts." Female spirits visiting men while they sleep for the purpose of fertilization is the definition of a succubus.
"One of the earliest mentions of succubus comes from Mesopotamia on the Sumerian King List, circa, 2400 BC, where Lilitu, a female demon, appears to men in their erotic dreams. Two other corresponding demons appear as well: Ardat Lili, who visits men by night and begets ghostly children from them, and Urdu Lili, who is known as a male counterpart to Ardat Lili and visits women by night and begets from them. According to Zohar and the Alphabet of Ben Sira, Lilith was Adam's first wife who later became a succubus. 
