Sheʾol and its synonyms, בּוֹר “pit,” שַׁחַת “chasm,” and אֲבַדּוֹן “oblivion,” was the fate of all people upon death. The wicked were sent there early, while the righteous were rewarded with a long life. During the Second Temple period, the negative attitude about death and sheʾol develops into a concept of post-mortem punishment and eventually hell. 1 Enoch’s four chambers for the dead is the first step in that direction.
According to the non-biblical book of Enoch, Genesis 6 tells of angels who bring sin to humanity, causing the Flood as well as sin and disease in the present.