Grahan Dosh is a situation when Sun or Moon comes in the same house with Rahu or Ketu in your birth chart, or at the lagna period. Rahu or Ketu are always moving in the opposite direction. Their attributes are also opposite to each other. Rahu denotes material desire, aggression, and passion. While, Ketu signifies moksha, detachment, and silence. Rahu and Ketu, like the other planets, are orbiting around the sun. It is during this revolution around the Sun or Moon that Rahu or Ketu can be in the line of the sun or the moon at one point of time. When this happens, mostly during a solar or lunar eclipse, the child will have a birth chart with Grahan Dosh.
Siddhi yantras can be kept at the place of worship in your house. You can also keep a Maha Mrityunjay yantra, Hanuman yantra, or a Rahu/ Ketu yantra at home.