A yantra is a mystical diagram that is the house in which a Devata (God or Goddess) dwells. Worship of planetary yantras is used to remove the ill effects of malefic planets and to increase the positive influences of favorable planets.
Shani is the God of Saturn and is one of the nine primary celestial beings in Hindu Vedic astrology who are the agents of the Law of Karma.
The yantra shows Saturn's symbol, the zodiac signs that Saturn rules, and mantras associated with the ruling deity, Kurma Deva. Saturn is traditionally the most difficult of the major planets. Saturn gives bad luck, misfortune and oppression. It is the planet of bad karma or unfortunate destiny.