According to Vedic astrology, Saturn is a hard taskmaster, who will hold us accountable for our deeds and misdeeds when we pass through the long Saturn transits that we will all undergo, at several times in our lifetimes. In Greek mythology, Saturn is known as 'Crones' and was believed to devour his newly born offspring, so that he would not be overthrown.
Reciting this Mantra in front of a 'Shani Yantra' will appease 'Shani Dev', or Saturn and to reduce the hardships that are experienced during his transits.