What is the name of the river that souls must cross to enter the underworld?

The river that souls must cross to enter the underworld is known as the Styx. In ancient Greek mythology, the Styx is particularly significant as it acts as a boundary between the earth and the Underworld. Souls, once they have died, must be ferried across this river by Charon, the boatman. It is often depicted as dark and murky, reinforcing the idea of the Underworld as a realm of mystery and gloom.

While the other rivers mentioned share significance in the mythology, they serve different purposes. The Acheron, for example, is sometimes associated with the river of sorrow, where the souls wait to be ferried across. Lethe is the river of forgetfulness, where souls forget their earthly lives before reincarnation. Phlegethon is characterized as a river of fire, symbolizing pain and torment. Each river plays a unique role in the mythological framework surrounding the afterlife, but it is the Styx that is specifically known as the crossing point for souls entering the Underworld.