In Greek and Roman mythology, Lethe was one of five rivers in the underworld, or the kingdom of the dead. Drinking from Lethe (whose name means "forgetfulness") caused the souls of the dead to forget all knowledge of their previous lives.
cult group bound together by devotion to a particular person, belief, or god
Some Greek religious cults taught their members not to drink from Lethe after they died. They believed that it was important to remember the mistakes of one's past lives so that, when reborn, one would be wiser in the next life. To avoid Lethe's waters, they told their followers to drink from a spring named Mnemosyne (meaning "memory") that was near the Lethe.
oracle priest or priestess or other creature through whom a god is believed to speak; also the location (such as a shrine) where such words are spoken
Springs called Lethe and Mnemosyne were located at a cave near the Greek town of Lebadeia. The cave, which contained an oracle, was believed to be an entrance to the underworld.