The person can speak and understand images more comprehensively than others, silence speaks louder to them than a room full of voices. Time may be spent in deep study, writing, and reflecting and they are happiest researching or spending time in libraries. Those with this placement have creative powers of the mind to tap into the collective. They draw from the collective all forms of art, symbols and music communicating knowledge in the deepest of ways. It is as if they have reached down into the bottom of the ocean and pooled their knowledge from below. The Neptunian and Pisces house is one of dissolution so the person is afraid on some level of being taken over by these waves of thoughts, and losing their mind to something much larger.
It is often a good placement for helping others to communicate, get their point across, or simply to listen. The person understands about being overwhelmed by an emotional force so large that it engulfs the ability to speak what they are feeling and these people can aid others across the choppy waters towards a clearer understanding. The person works beautifully when involved with dream-work, psychology and understanding the unconscious.
Sometimes they suffer from too much information drifting into the mind and must learn to shut out the thoughts of others, to know what it is that they think. They need to guard against intruding thoughts from others in order to clear their own mind. The person with Mercury in the 12th house may feel that others misrepresent what they are saying, and confuse matters. The individual may be prone to mental anxiety and worrying too much, and trying to unconsciously control the chaos by being super organised. However, sooner or later everything may feel as if it has all fallen apart again. Sometimes Mercury in the 12th house shows up physically in the individual and they could have a learning disability, hearing problem, or speech problem preventing them from being truly understood. This may leave them feeling disconnected from reality, people and places, and feeling so out of the loop they may feel highly vulnerable about their mental capacity.
The person may also feel their thoughts are too dis-organised, overwhelming and there is too much information making it difficult to gain clarity. They are so attuned to the inner experience, and hiding their thoughts that it may be hard for others to understand. Maybe there is a large tendency towards fantasizing, imagining, and drifting off a lot of the time. They just need to sift through a lot of the past and understand it to be as present as they can be. Mercury in the 12th house reflects a great talent in writing, speaking in regards to the intellect. However, there is always a struggle and the person may have to first untangle the feelings of why they feel so inferior mentally, and how their upbringing may have some part to play in the condition of their thinking.
Perhaps they were bullied for speaking or for not talking, told to be quiet all the time. Perhaps every time they expressed themselves verbally they were quickly made to feel their ideas had no value. They may have learned not to talk about personal matters and feared saying anything at all. Much of this anxiety can be channeled through communicating their deeper insights in some way, and realizing that these perceived weaknesses may actually be hiding their greatest strengths.