The twelfth house is a closed house, the house of solitude and immersion in oneself, in one's inner world. The twelfth house is symbolically the house of Pisces, the ruler of which is Neptune, so this position for the planet is considered strong. But there are nuances, as Neptune manifests itself in two very contrasting opposite poles. Let's consider it in more detail...
With this position of Neptune, the person has a pronounced intuition, hypersensitivity and hyper-receptivity, they are inclined towards spiritual experiences, and they very subtly feel the energetic and emotional vibrations.
Another manifestation of Neptune is creativity. And therefore, the owner of such a Neptune also has a strong dreaminess, they have an unconscious sense of unity with the whole Universe and a desire to dissolve in the general flow of life. Such a person is often immersed in the world of fantasies, ideals and spiritual searches. And accordingly, they may have a strong attraction to art, music, literature, to mystical knowledge.
In a positive way, Neptune gives such abilities as clairvoyance, clairaudience, the ability to receive important information in a dream or to sense the approach of a particular situation. It's hard for them to explain this: the knowledge that something should happen comes by itself. Neptune is the significator of our grandmothers and grandfathers, and indicates the ancestral connection with them. Therefore, often with such a position of the planet, abilities can be inherited from grandmothers or grandfathers, or they come in a dream, prompting and guiding when a question or a difficult situation arises.
Neptune in the 12th house inclines the person to the desire to spend time alone or in solitude. Often, such a person is good in monasteries, in some quiet, peaceful place or near water. In this space, they feel calm and, being in it, they restore their thoughts and their inner state.
In a negative manifestation, such a person strives for a constant state of relaxation, a life of only pleasure, and unconsciously seeks out areas where they don't have to strain. And there may also be a craving for all kinds of addictions, especially if the natal chart of the person is complicated or tense.
There are also such contrasting situations when, due to hypersensitivity, the boundary between the real and imaginary worlds is blurred, which can lead to mental disorders.
Also, a person with such a position is susceptible to deception and can become a victim of deception or manipulation due to their tendency to believe everything.
The 12th house also responds to chronic diseases, so with this position of the planet, there may be tumors, problems with lymph, blood (Neptune is responsible for all fluids in the body), and a weakened immune system.