Dusthanas and Dasha period.

A benefic planet in a dusthana house (6, 8, 12) will weaken the good
effects of this planet. They can cause problems associated with the
areas these houses are indications for. Disease, enemies and legal
problems can surface in the sixth, obstacles with finances, chronic
health problems leading to surgery for the eighth house, and
hospitalization, retirement or imprisonment for the twelfth house.
These all become relative during the dasha of a benefic planet placed
in a dushana house. A benefic planet in these houses with a malefic
planet aspecting it further produces these ill effects all the more. Since
the 8th and 12th houses are moksha houses from the difficulty arises
spiritual realizations, leading to spiritual liberation, the purpose of life.
Malefics in dushana houses are the most problematic of all. They will
cause some suffering and ill health. The 6th house will give the
motivation to overcome things because it is a upachaya, but the 8th
and 12th will cause great difficulties involving losses and possible
deaths.