Kaal Sarp Yantra on Bhoj Patra. ‘Kaal Sarp’ is an astrological condition, which is formed when all the planets are situated between Rahu and Ketu. Rahu is known as snack and Ketu is its tail. The person who takes birth in this yoga suffer from various problems. The Kaal Sarp Yoga is a dreaded yoga that can cause one's life to be miserable.