By the time we reach Pluto, we are already very deep into the subconscious where things have become so instinctual, immaterial and psychic that words fail us. And when words fail us the result is subterranean intensity, frustration, suspicion, conspiracy, power struggles, obsessions. Pluto is the planet of cathartic death and rebirth through purging, destruction and elimination.
Psychoanalysis was discovered around the same time as Pluto. Psychoanalysis is a process of diving deep into the subconscious to dig up all that has been unexpressed, and eliminate all that has been pent-up so that the patient can start afresh.
Austrian neurologist Sigmund Freud, the father of psychoanalysis, treated patients that had various physical ticks but digging deeper, he discovered that these outwardly visible ticks were the result of psychological issues trapped in the subconscious. Ticks were traumas' roundabout ways of expressing themselves. The therapy included asking the patient questions to make them go deep into the root of the problem and bring that trauma into conscious understanding. That is when the healing happened. The problem had to be discovered, verbalized and expressed in order for healing to begin. Thus also Pluto's association with secrets, intensity, mental power and self-knowledge. Of note, Pluto was demoted in 2006 from a planet to a dwarf planet which reflects the power struggles that Pluto is also associated with.
The central aspect of the Plutonian personality is that the veil, the membrane, between the conscious and the subconscious is thinner and visions, memories, thoughts pass through it much more easily. On one hand, this is a good thing - you understand the real nature of human motivation much more easily, thus having insider information and immunity to lies and delusions. On the other, the membrane is there for a reason. It protects sanity and preserves social conditioning and communities in general.
A strong Pluto in the chart graces the chart holder with powerful psychoanalytical skills. Many people can "read" other people on an energetic level but the extent of Plutonian power goes further than that. Pluto senses, analyses, investigates and acts. Sensing other people out without being able to explain in words or even fully consciously understand the good or bad "vibes" someone is giving off is a low ball for Pluto.
This planet understands the pattern of behavior and the inner logic of someone's actions. When someone understands you on that level, you feel naked and as a result a feeling of discomfort, even shame, tends to creep in. This unauthorized knowledge of "shame-inducing" psychological processes, this ability to see people naked all the time, gives Plutonian people their signature aura of mysteriousness, darkness and intensity. When they look at a situation unfolding they don't look at what is happening on the surface (who is saying what), they look at the undercurrent of needs and agendas that are being negotiated.
In Hellenistic mythology, Pluto (Hades) was the God of the Underworld, the place where all those who had infuriated the gods were sent to repent. Interestingly, this wasn't a place of torture, blood, fires and screams, as Hell is often described to look like. It was a place where those who had made grave mistakes were thought a moral lesson in ways that were punishing but not necessarily physically torturous. In other words, the underworld over which Pluto presided was much less a place of torture than it was a place of moral justice.