The Book of Orokiah is a book passed down the lines of the annointed ones in order to instruct them on how to defeat Azazeal and the other Nephilim. The book contains a series of prophecies on what will happen when the child of Azazeal is born as well as ritual on how to defeat the fallen angels and their offspring.
"Look toward the setting sun,
Even to the western skies;
Where the clouds gather
And Azazeal's whore grows great with child."