Monkshood roots. Roots of common monkshood (Aconitum napellus), a plant used in herbal medicine. Monkshood roots are believed to have analgesic (pain-relieving) and sedative properties. They are used as a tincture (spirit solution), syrup, or fluid extract. However, monkshood is also very poisonous when taken in the wrong dosage: it paralyzes the body's nerve centres and can, in extreme cases, lead to death.