The Grigori (AKA
watchers, AKA
Irin) are a borderline non-canonical (and at least not talked about in the mainstream branches of Christianity) branch of fallen angels that were sent to earth to watch over humanity in the time of Jared (a rough estimate would put that around 3000 BCE) and
went native.
They had twenty leaders, each leader leading a group of ten.
(Leaders include
Shemyaza,
Arakiel,
Azazel,
Kokabiel,
Tamiel,
Ramiel,
Daniel,
Chazaqiel,
Baraqiel,
Asael,
Armaros,
Batariel,
Ananel,
Saquiel,
Shamsiel,
Satariel,
Turiel,
Yomiel,
Sariel and
Bezaliel, who gets left out of most translations because his name was so badly damaged in the transcripts.)
They pop up (potentially, as like with most things in the Bible, people have different interpretations) in Genesis six:
"When men began to multiply on earth and daughters were born to them, the sons of God saw how beautiful the daughters of man were, and so they took for their wives as many of them as they chose. Then the Lord said: "My spirit shall not remain in man forever, since he is but flesh. His days shall comprise one hundred and twenty years." At that time the Nephilim appeared on earth (as well as later), after the sons of God had intercourse with the daughters of man, who bore them sons. They were the heroes of old, the men of renown"
Source
(The ambiguity comes in with just saying 'sons of God', rather than saying 'fucking angels, man').
Again (possibly) in Daniel 4:23:
"And whereas the king saw a watcher, a holy one coming down from heaven,"
And then again the Book Of Enoch that was found with the Dead Sea Scrolls. The book of Enoch actually has the story of how they fell in lust with human ladies, 'got married' (
ahem), produced "giants" (about six feet tall, but that was impressive back then), and started teaching everybody things Man Was Not Meant To Know(tm).
Hanky was pankied. We learned about things like '
makeup' and '
weapons' and '
magic' and '
writing' and '
astrology', they learned about sex and booze and more sex and more booze and, hey could you top off my glass? Thanks.
This didn't go over well, especially when their offspring, the
Nephilim, started ravaging the countryside and craving
human flesh.
"Then Michael and Gabriel, Raphael, Suryal, and Uriel, looked down from heaven, and saw the quantity of blood which was shed on earth, and all the iniquity which was done upon it, and said one to another, It is the voice of their cries; The earth deprived of her children has cried even to the gate of heaven."
Enoch, chapter nine. source
The leaders were all heavily smitten, with each one being blamed specifically for all the crimes their actions lead to (for instance, Azazel taught men about weapons, meaning every single act of bloodshed done with those weapons in now on his head. He did not get a happy ending). Everyone else was trapped 'under valleys' until the end of the world rolls 'round. All the nephilim were drowned in the great flood Noah had to put up with. (Well,
probably all of them.
We think).
The thing you should be taking away from all this isn't "How stupid do you have to be to be drinking/canoodling on the job when your boss is omnipotent, has a hair-trigger temper, and a cache of lighting bolts?" But that:
Yes. Humanity managed to corrupt a flock of angels. We are just that
awesome.