How does the Book of Enoch describe the origin of evil?

The Book of Enoch describes the origin of evil as the descent and rebellion of the Watchers, two hundred angels who bound themselves by oath to take human wives. This act, set on Mount Hermon, unleashed corruption upon the earth through their unions and the forbidden knowledge they shared (1 Enoch 6).

From those unions the giants were born, who devoured the earth and filled it with bloodshed, while Azazel taught humanity forbidden arts that spread further wickedness (1 Enoch 7; 1 Enoch 8). The archangels beheld the resulting violence and carried the cry of the oppressed to heaven, prompting the pronouncement of judgment that bound Azazel, chained the Watchers, and promised the cleansing of the earth (1 Enoch 9; 1 Enoch 10).

In this way the Book of the Watchers presents the origins of evil not as an abstract force but as the concrete consequence of angelic rebellion, the birth of the giants, and the corruption that followed, a narrative Enoch himself is commissioned to announce (Book of the Watchers; Characters - Characters: Enoch).