A very powerful yantra for the worship of Goddess Kali is the Mahakaali yantra.
This Yantra has occult powers – its worship reverses the ill-effects of black magic, and frees a person from the bad influences of spirits & ghosts. This Yantra also eliminates the harmful effects of malefic planets, especially Saturn, which is usually responsible for misfortunes, sufferings and sorrows in life. Kaali Yantra bestows spiritual power, and results in fulfillment of desires, increase in wealth and comforts of life.
This Yantra is also a time-tested remedy against chronic diseases like blood pressure, paralysis and nervous disorders. It also bestows longevity to the person who wears this Yantra on his body.