Related Clues:

• Nighttime visitor of folklore
• It can knock you out
• Potent drug
• Tranquilizer
• Lethargy inducer
• Sedative drug
• Endorphin, e.g.
• Drug that dulls the brain
• Drug from poppies
• Poppy derivative
• Morphine, for one
• Narcotic drug
• Endorphin, basically
• Mind duller
• Religion, in an oft-quoted metaphor