Possible Clues:

• Underworld river causing forgetfulness to all who drank it
• French and English articles inducing forgetfulness
• River overcoming all but the elephants?
• River in 'The Divine Comedy'
• River in "The Divine Comedy"
• River obstruction fixed by explosive
• Classical river of forgetfulness
• In Greek myth, the river of forgetfulness flowing through Hades
• One must allow he is most forgetful
• River that causes people to forget