Angel Orders:

Grigori : They were given the responsibility to teach mankind. But they got attracted by human women and fell from grace in having sexual relationships with them. The offsprings from these combinations were the Nephilim, evil and fierce giants. After their descent to earth the Grigori were never allowed to enter Heaven again. Their leader was Shemyaza. As far as I know, Shemyaza is NOT Luzifer ! That brings me to the point, that in The Old Testament, angels were not always joy, mercy and heavenly love ! God was sometimes revengeful in those books, and so his angels were fiery creatures with flaming swords. The idea of angels as beings-better-not-to-be-angered is very old, and some of them have had quite a few all too human flaws.