Pluto in the 12th house feels a bit disoriented and confined in the physical world, because the soul intent is to merge with the universal and the timeless. There may be a tendency to live in the fantasies and/or trying to escape the reality.
Pluto here is extremely receptive to the concept of suffering, and whether you have been personally involved in a traumatic event or not, your intent is to learn how to be attuned to the concept of suffering, ultimately giving you a very high capacity to understand, feel, and channel humanity's pain.
The 12th House is collective, it is what is unspoken yet common to every human, it is being capable of talking to masses, to a collective, through your capacity to channel this essence that everyone can relate to. Often this is seen in people who have a work to do with the unconscious, with the collective, and often we find people involved in arts, in politics, in social causes. The 12th house also rules what is unconscious, invisible, ungraspable. It covers a wide range of subjects, from your own subconscious and invisible things that control you or influence you within your psyche, to secrets and undercover things. I like to sum up the 12th house as the collective unconscious though, all the unspoken and invisible things that are common to all humans. When you tap in the 12th house, you can touch, speak, influence any other human, because you're touching on archetypes that everyone, even unbeknownst to them, can feel and understand as something that they experience too.
There is always two path possible - the high & the low path. In its highest expressions, Pluto here is going to seek to understand & channel the collective, by creating, by transforming pain into art, by transforming pain into global change for a given collective. Here Pluto seeks to understand what's unspoken & invisible, and there is a tremendous capacity for self-awareness and reflection.
Pluto in the 12th house seeks power through the collective and through unspoken/invisible things. Typically with this position of Pluto we find people whose power is particularly underestimated, an invisible force (Hello Donald Trump). When your Pluto is located in the 12th house, your power is your capacity to influence others by your grip on collectively unconscious things. To go back to Trump's example, whatever your opinion of him is, he managed to get elected without any political experience, because he managed to make American people resonate with him. He tapped in the collective subconscious, and that is indeed what Pluto does in this house.
With this position of Pluto we find politics for sure, we also find artists, mystics, spiritual personalities, but the common thread is always the same: People who are tapped into collective vibes, collective archetypes. Art has this capacity to speak to any human, regardless of their political ideas, their culture, their language, anyone can be touched and moved by art. This, is the collective.
The 12th house seeks to elevate. That is the intent of Piscean values, transcending human separation through individual bodies and ego, and achieving oneness by cultivating awareness of oneness and transcending limitations and separation. But you know what else happens when you seek to escape your human body and individuality and attempt to achieve merging with humanity? You also tend to escape your own set of personal problems, your own set of struggles and pain. The 12th house elevates, but this is muddy territory.
As much as spiritual oneness is a valid concept, it's easy to get into a habit of escaping your own self, and that is something that Pluto in the 12th house can be tempted to do.
As always with Pluto, repulsion and attraction is at play, as well as obsessive and compulsive tendencies. As the 12th house rules less noble things, such as self-undoing, escapism in all its forms, there can be a tendency to compulsively seek to escape your own pain.
Pluto in the 12th house is compelled to achieve a transcendence and elevation process. This is a life spent cleaning up your own spiritual closet. This is your mission, should you choose to accept it.
"Pluto an evolutionary journey of the soul": By Jeff Green
"The book of Pluto": Steven Forrest
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