Kantaka Sani means Saturn behaving like a thorn in the leg and the person has to limp in all activities of life. Profession/Career is hampered and finances dwindle. The transit of Saturn in the 1st, 4th, 8th and 10th signs either from Lagna, Arudha Lagna or the Moon sign cause Kantaka Sani to operate.
When it happens:
1) With respect to Lagna, the person makes wrong decisions and suffer due to that Lagna is our intelligence, our Dhi.
2) With respect to the AL, the career and finances are greatly affected because Arudha lagna is shoving how society perceiving us. It is like reaction toward the world, how you surround with the world.
3) From Chandra, the person suffers physically and emotionally because Chandra is our Manas and also represents the Sharira (body).
When Shani is placed on Lagna, he is in Marana Karaka Sthana and it will destroy person’s intelligence. When he transit forth house the cure will be denied because the fourth house is the house of healing. Shani in eight houses couses lot of transformation of the body. It is good for the healt. During that time is horrible, but after is very good. It is like in story about Kurma Avatara and the time when Devas are turning of the ocean. That is what’s happend when Shani trasits eight house. Lot of poison will come up but Amrita will also came in the end. So when Shani is in eight house it couses all this problem in the body, and if the body if not strong person could die during that time. From there he aspects second house cousing bad food come into the body and a person eating wrongly and it is aspecitng fifth house, person is doing wrong mantras and he aspects the tenth house, that is what is Kantak Shani. It is when he aspects tenth house. Then the persons Karma yoga is destroyed. That is why it is worst transit. It is damaging all these other places and damaging the Karma yoga.