The twelfth house is probably the hardest house to deal with, since it's hidden behind the ascendant. It's psychology and motives is really hard to find, beeing a "water-house" - very unpersonal and maybe the place we meet God and the forces behind our lifes.
We have discovered the psychology in the other "water-houses" - especially the fourth house - but also the eight house. Here is death an issue, but in the twelfth house our fears and opponents are more of a divine character.....and it's forcing us to develop our very souls.
The twelfth house brings disorder to what the sixth house have made order in, and in the twelfth we have to put aside our ego - which we have used so much power to strengthen in many of the other houses.
It's here the circle ends, where we go back to the beginning. And we must face our higher self, which is a part of the divine source that life's coming from. It's like a judgement, where we lay our lives in front of the jury.....which is God or our higher self.
For example, in christianity Jesus says something like "if you're not true to me, that will be forgiven - but if you're not true to the holy ghost, that will not be forgiven."
What I mean is that we have to be true to our higher self, which is the pure spirit we originally were given. In the twelfth house we meet this pure and divine source, and if we're not true to it, we will suffer from the pain of transformation.
This is why so many feel lonely, or is isolated or in other ways are taken away their freedom.
But the twelfth house can on the other side also be a great and a happy place to be, if we just listen inside and understand that we are a part of a divine plan with higher love, hidden answers we can reveal and a path to heaven if we lay our ego aside and seek the truth and light inside from our higher self.
I have Saturn retorgrade in twelfth house and Pisces, and when it returned when I was about 30 yrs, I was sick with a mental illness. I stayed out of the hospitals, but changed totally from who I was. I discovered a higher meaning of life, but also I went through some tough times that transformed me into a person I liked much more than the person I used to be.
I'm glad I have an active twelfth house in my horoscope, because it gives me an opportunity to meet God and develop myself and my soul to a higher level.
Well, this was some thoughts I had. It's based a lot on my own experience with the twelfth house, but I hope others can find something eatable here too.