An initiation (a rite of passage into adulthood) frequently involves pain, but it also involves a new birth. Let’s take a literal example: Sometimes transiting Pluto to an Angle correlates with a time that a woman gives birth to a baby.
There is something that happens to the psyche of a woman when she gives birth: it’s as if after experiencing the extreme pain and the sacred process of birth, she becomes a lot stronger, more confident, almost a new being.
This makes me feel that giving of birth is a kind of initiation for a woman* (I believe there are more ways in which a woman can go through similar process in order to gain strength without actually giving birth.)
So some pain can serve as initiation – the kind that will let you experience the depth of your soul through sheer terror, grief, or rage: in short, extreme, Plutonian pain. But pain without purpose becomes mere cruelty and abuse. To serve as an experience of initiation, there needs to be a sense of meaning and higher purpose to the pain.
This suggests that we will have a better chance of going through the pain of psychological healing if we understand the ultimate purpose behind the work – to regain wholeness of the soul. Same goes for overcoming addictions – when the work becomes about healing the primal wounds and lack of love that led to the destructive behaviour, the work begins to gain meaning despite the pain. Anyone that went through the underworld of their soul through such works comes up stronger and more individuated than before.
So what kind of measurements suggest the need for initiation? Natally, any place Pluto is in may be your entrance into the Depth. I have Pluto in 7th house, and this means I tend to attract partners that have gone through the Plutonian process described above, and/or relationships basically tend to put me in the underworld (help!) I’ve seen it happen both ways – in general relationships encourage me to go deep into my healing process, and I’ve come a long way in healing my soul through them.
Natal Pluto in 8th house often suggests that you’ll gain a lot of benefit from psychotherapy and other similar processes. Pluto in 9th may suggest that the issues around your core religious beliefs and worldviews may cause you to slip into the Underworld, when those beliefs are shaken.
Pluto in 12th may mean the path to the underworld is hidden from you – which is to say you may have a hard time staring into the depth of your soul, making you feel like a stranger to yourself – until you completely surrender your need to control (which seems to be a key for many 12th house placements.)
Pluto transit to the natal hotspots (Angles and planets) may trigger an initiatory experience, especially if the 8th house is also involved. It doesn’t have to always mean pain – it can be a profoundly inspiring experience – but if it happens to come with pain, try to find the meaning behind it.