Summary: This stimulates the imagination and intuition. A good time for a spiritual retreat. If Mercury makes difficult aspects, watch out for subconscious mental distortion and potential health issues.
This interpretation is for when Transiting Mercury is going through your natal twelfth house.
In general, the 12th house has to do with a perception, with a psychological awareness of the content of the subconscious, as well as secret communications and investigations, psychic practices and/or intuitive perception. During this period it is possible that a powerful energy arises that has to do with the intuitive channeling of information from a higher source, because it is evident that when Mercury is in this position, the mental aspects of the imagination will be strongly stimulated.
It is a good time to meditate, and it might be a good idea to go to an ashram or take a retreat. You may come into contact with hospitals, institutions or prisons. If Mercury makes difficult aspects, there may be subconscious mental distortion, escapism tendencies, and in extreme cases it may affect health, so you should watch it.