IMHO, They are indeed very real.
Their existence nicely ties together numerous Old Testament and New Testament passages, themes, and doctrine regarding those who attempt to abrogate the Plan of God by substituting a counterfeit for man to assume His blessings.
God is not mocked and knows all from the beginning.
Other buzzwords which tie them together are from extra biblical texts, such as the Book of Enoch and archeological discoveries of Monoliths, Pyramids, human sacrifice, and evil spirits without bodies.
and many Christians poo poo The Book of Enoch but I don’t think it contradicts the Bible
The Book of Enoch points to Jesus