Mercury in the 8th house revels in discovering what is concealed and the more forbidden a subject, the more likely they will want to penetrate the matter in question. It may be macabre, perverse, or controversial, but the mind is less unflinching and undaunted by such studies and they are very resolute in their interests. In some cases, those with this placement have been involved in communication with the deceased, and subjects beyond the grave don’t frighten them.
Mercury here has the ability to pick up the unspoken words of others and tends to miss nothing, reading the subtle cues in the environment. If you verbally attack them, they have counter psychological missiles on hand to destroy and know how to be sarcastic or verbally wound. If they walked into a room of people gossiping and suddenly everyone shut up, they know exactly who they were talking about. Mercury in the 8th house has feelers for hidden information and secrets cannot be hidden for long.
On other matters involving the mind, they might enjoy sharing their ideas and perceptions with a partner and possess a fundamental curiosity about things when experiencing close emotional connections with others. Typically, bonds are formed with others through sharing personal secrets or talking about shared pain or trauma. However, they can go for long periods in silence, but if they have something to say they will get in touch, and can often relay thought provoking ideas to others, and in very few words.
On matters involving communication and intimacy, they may seek to understand the deepest motivations of others through psychology, and this may be a person who helps to talk people through disturbance and crisis, exploring the taboos of life in depth. In general, they may be drawn towards extreme styles of speech, and always have something profound to say, teach or write. Mercury in the 8th house is good at analyzing the exchanges between people, and this is the mind of the detective, occultist or investigator with a deep desire to know as much as possible. Moreover, they make perceptive, insightful and intuitive writers, and there may also be an interest in sexuality, evolution, shared resources, financial deals, taxes, occult, psychic activity, or death. In a few cases it may indicate the death of a sibling, or conflicts involving inheritance, or the unthinkable aspects of life.
Mercury in the 8th house is focused on the darker side of life, and they have to be aware of a tendency to control others intellectually and may be prone to mental paranoia and a suspicious nature. Mercury in the 8th house can be very secretive, and the mind is very determined and unflinching and they need to communicate on a deep and meaningful level. This position of Mercury might be associated with a black sense of humor and highly sophisticated one. Astrologer Sue Tompkins links this placement to ‘heavy breathers ‘on the telephone and phone sex!