Marana Karaka Sthana (MKS) literally means Death Signifying House.
Marana Karaka Sthana is a house, where the contribution demanded from a planet via his placement, is against the fundamental nature of the planet. Because of this reason, the planet becomes very uneasy and feels like dying rather than contributing to such responsibilities of the house.
Shri Vaidyanath Dikshita in Jataka Parijata has taught the concept in Chapter 17 of Kalachakra Dasa. He has listed the Marana Sthana of 8 planes from Sun to Rahu. If natural malefic planets in weakness (debility, enemy sign, etc) are conjoined with or aspect a planet in Marana Sthana then there is greater suffering.
Marana Karaka Sthana or Death Signifying House(s) for different planets are as follows:
For Sun: Marana Karaka Sthana is 12th H
Sun is the king and his placement in the 12th House of compromise and giving up is MKS for him. Because a king is very uncomfortable giving up all his belongings like kingdom and wealth etc.
For Moon: Marana Karaka Sthana is 8th H
Moon is the mind and likes to dwell & enjoy in the material world, when he comes in the 8th H of longevity/death he becomes very uncomfortable with these very thoughts and he feels like dying.
For Mars: Marana Karaka Sthana is 7th H
The planet of war, dominance, and aggression when told to contribute to romance, love and sensuality becomes very uncomfortable in 7th H.
For Mercury: Marana Karaka Sthana is 7th H
Also, Mercury being a eunuch planet, when contributing to marriage, honest partnership, and procreation becomes very uncomfortable with the situation in 7th H. He likes to experiment, have fun and enjoy.
For Jupiter: Marana Karaka Sthana is 3rd H
Jupiter the planet of righteousness, world peace, and wisdom, when has to do aggression and take weapons in hand in the 3rd house, becomes very uncomfortable.
For Venus: Marana Karaka Sthana is 6th H
Venus the planet of love, sensuality, and passion is at great unease in the 6th house of celibacy, separation, and fights.
For Saturn: Marana Karaka Sthana is 1st H
Saturn the significator of disease, suffering, and sins, when delivering health and character to a person, becomes very uncomfortable in the 1st House.
For Rahu: Marana Karaka Sthana is 9th H
Rahu the planet of cheating, deceit, and irreligiousness when works for righteousness (dharma), guru, temple (religious place), etc becomes very uncomfortable with the work.
But one must do his karma no matter what the situation is, and so must all planets do in a chart. Consequently, the following important things happen:
1. The houses owned by the planet suffer terribly because the lord (owner) is not able to care for and contribute to his own house(s). He is too occupied with the work he hates in Marana Karaka Sthana (MKS).
2. The Naisargik Karak Tatwa (Natural Significance) of the planet suffers and it becomes negative or problematic for the native. The native suffers at Naisargik Karak level, at one point in life.
For example, Mars is Naisargik Karaka (Natural Significator) for younger brother, land, property, aggression, fire, initiative, engineering/engineers in general, police, security, army, logic, simple machines, etc. If Mars is in Marana Karaka Sthana (MKS) then the native suffers in one/some of the areas at some point in life.
3. When a planet is trapped in a house he hates and he is told to do something repeatedly he abhors, he becomes very disturbed and continues to do and behave according to his basic nature. Consequently, at the very core, the planet behaves negatively for the house it is placed in i.e. in MKS.
So every planet depending upon its inherent nature reacts differently. The natural malefic planets (kroora grahas) like Mars, Saturn, Rahu, and Sun retaliate in a harsh way and therefore marriage/relationships 7th H, health/character/ideas (1st H), dharma/luck (9th H), attitude to compromises/ give up/bed pleasures, etc (12th) suffer severely.
Natural benefic like Venus, Jupiter, Moon, and Mercury behave in a somewhat kind way but all do some bad to the house where they are placed in MKS.
Sun is the King and gives work to all in the society. Sun is also the giver of wealth (in the form of 12 Adityas he gives us everything). If Sun is in Marana Karaka Sthana (MKS) in Rashi or D-10 then at some point in time there could be no work/wealth/Boss for the native considering other factors are also negative for these aspects. It can also cause a huge loss of wealth at some point in time for a native.
To be continued with example charts and remedial measures …