Composite Mars in 12th house can refer to a relationship where not all actions and intentions are always clear to everyone involved.
Suppressed or unconscious needs
The 12th house signifies what is hidden, unconscious, in the subconscious, as well as ideals and fantasies. With Mars located there, it brings forth themes where actions, aggression, sexuality, motivation, and goals are somehow suppressed. When energies are suppressed, they cannot manifest directly in the external world. When energies don’t manifest externally, they turn inward and remain hidden, or depending on the degree of suppression, they can even be unconscious. For example, a person might have learned to suppress their desires and will as a child due to feelings of shame and guilt..
Composite Mars in 12th house relationships
In the context of a romantic relationship (or any relationship, really), this setup doesn’t sound easy at first. Generally, it’s not advisable in relationships when not all parties are aware of the other person’s intentions and goals. How this manifests in each relationship can vary greatly. For example, in a friendship, one person may have a secret hobby they keep hidden. In a romantic relationship, this configuration might indicate difficulty expressing sexual desires or an extramarital affair.
Unclear sources of conflict
This configuration can also manifest in more vague ways. In a romantic relationship, couples might have various conflicts with unclear sources. Subconscious values, desires, and goals can influence the thoughts and interactions of both parties. After a long enough argument and discussion, the couple might eventually realize that they were actually in agreement about the subject of the dispute. They might not have been able to communicate it clearly and understandably to each other. In this case, it’s crucial for the couple to prioritize clear communication of their views and thoughts to one another, and for the partner to genuinely understand each other.
Mutual spiritual and artistic goals
Setting aside the everyday problems in a romantic relationship, this composite chart placement can also manifest in people who share a common goal related to the themes of the 12th house. For example, both parties might have a shared spiritual, artistic, idealistic, subconscious, therapeutic, or similar goal. This configuration also grants a great capacity for acceptance and forgiveness between the individuals in the composite chart.
As always, when considering the placement of planets in houses, the aspects of Mars to other planets and the signs they are in also play a significant role. For instance, a Jupiter trine Mars would generally provide a more positive push for Mars in the 12th house. However, if Mars is unwilling to come out of the 12th house, Jupiter’s expansive influence might lead to even greater idealization and unrealistic fantasies.