Related Clues:

• Religion, to Karl Marx
• It may induce relaxation
• Sedative
• Drug
• Mind boggler
• It can knock you out
• Potent drug
• Lethargy inducer
• Sedative drug
• It may be found in a den
• Endorphin, e.g.
• It's addictive
• Drug that dulls the brain
• Drug from poppies
• Poppy narcotic