This is another less known or I should say less used concept of Vedic Astrology, may be that's why it is getting posted so late by me. But better be late than never.
So, every planet is karaka of few houses in Astrology, it means it is significator of things related to that particular house. Below is the list of the houses and their karaka planets -
1st House - Sun
2nd House - Jupiter
3rd House - Mars & Mercury
4th House - Moon
5th House - Jupiter
6th House - Mars & Saturn
7th House - Venus
8th House - Saturn
9th House - Jupiter
10th House - Sun-Mercury-Jupiter-Saturn
11th House - Jupiter
12th house - Saturn.
Now, this concept of Karaka-Nasha Bhava, as it is spread, suggests that if a planet is sitting in the house, which it is karaka of, then it destroys the results of that house. Like, if Jupiter is sitting in 2nd house, it will destroy the Family and Wealth or if Venus is in 7th house, it will destroy the relationship aspect of life.
Even prima-facie, this concept, as stated above, doesn't go down the throat so easily. As always, things in Astrology are far deeper than they look or spread out.
So, it goes like this that if a planet is sitting in the house, which it is karaka of, then as always check the dignity and basic nature of planet. If planet is in good dignity (exalted, own, mool trikon, friendly or neutral sign), then it will not only protect the house but will also give benefic results. Even if planet is in bad dignity (enemy or debilitated sign) but if planet is benefic in nature, it will still provide something out of that house, if not 100% then at least 25%, because the nature of benefic planet is to provide. They are not supposed to take away things.
Like, if Jupiter is in good dignity in 2nd house, it will certainly give benefits of 2nd house of wealth and family. If it is debilitated in 2nd house, then also it means person will get Wealth from Mother or Real Estate (as Jupiter would rule 4th house) but he won't be able to save it and will spend it unnecessarily. So, its not that Jupiter totally denied the results of 2nd house. It still gave the wealth but not the wisdom to save it.
Even a malefic planet in good dignity will give good results of the house which it is karaka of and sitting in. Like if Mars is exalted in 6th house, it will give immense courage to fight against enemies, best example - Sachin Tendulkar's Chart (http://astrosaxena.com/stendulkar). Likewise, if Saturn is in Libra in 8th house, it shows someone working in Secret Agencies for Govt and with great Authority
The real problem comes when a Malefic planet is in the house, which it is karaka of, but it is either debilitated or in enemy sign, because then not only planet's dignity is wrong but also its basic nature is malefic. In that case, it only knows to take away things if not supported by other planets through conjunction or aspects or Yogas. Like if Mars is debilitated in 6th house or Saturn is debilitated in 6th or 8th house, then we need to check for the support this planet may be getting from different Yogas and Planetary Combinations.
So, the steps involved to check the applicability of this concept are as follows -
1. Look at the dignity of planet. If dignity is fine, there is no Karaka Nasha Bhava.
2. If debilitated or enemy sign, with no other support, then Karaka Nasha Bhav applies.
3. Even if things are as told in point 2, a benefic planet will still give some benefits related to that house as it is its nature to provide.
4. Real problem comes when a malefic planet in wrong dignity sits in Karaka Bhava. Then it depends on other Yogas and Planetary Combinations for good results.
Hope this helps and understandable.
Vishal S Saxena - Astrologer
Website - www.astrosaxena.com
Facebook Page - https://www.facebook.com/astrovishalsaxena/
Twitter Page - https://twitter.com/astrovsaxena
Mob - 7207658536