The daughter
of Eris, Lethe was the
goddess of oblivion and the river with the same name. When someone died and
went to Hades, they had
to drink from her water so hey would forget their previous existence on earth.
If ever anybody was allowed back to life, again hey had to drink from the
river so they would not remember the afterlife.
Lethe was the sister of Thanatos (death) and with Zeus
she had the Graces/Charites.
According to some myths she was the mother of Dionysus.