Possible Clues:

• Flower, deep in the ground, no forget-me-not!
• Woman's last to surface — drink has a profound effect here?
• One of the five rivers of Hades, causing forgetfulness in those who drank from it
• River whose waters caused the souls of the dead to forget completely their life on Earth
• Hades river
• Underground flow of water coming from toilet here
• Allow that man to find oblivion
• River of the underworld
• "The Divine Comedy" river
• Infernal flower?