Even though there is a 1st House in the chart, a circle really has no such thing as a beginning. So, in a way, the 12th House precedes the 1st. What can we say about something that precedes birth, advent? What existed before the flower burst (Aries, 1st house) through the earth (Taurus, 2nd house)?
The kernel in the soil. It's invisible, but it holds the potential for life.
That is why, since the 12th house rules the potentials that existed prior to our coming into existence, it is associated with karma.
Planets in the 12th House behave a lot like kernels in the soil or babies in the womb: they develop in the dark - hidden and invisible. They dare not come forth.
These planets are often reluctant to become integrated parts of our psyches because they feel they aren't ready to be born, to be seen, to emerge into the "real world".
All humans are born premature. It takes years for us to become independent and develop fully.
Planets in the 12th House feel the same way - overwhelmed by the chaos, tasks, and responsibilities of the world.
They retreat into solitude, invisibility, and the unconscious.
That is where the association of the 12th House with asylums comes from.
Actually, this is just the most common one, but this house is really connected to all places of seclusion, solitude, or exile - and all abandoned places.
All places where we can heal, retreat, or develop in the dark and unseen - like a kernel in the soil. Like a person in hospital, in an asylum, in prison, detention, foreign countries,....
Any planet in the 12th house is basically abandoned and neglected.
It's a kind of self-deception and self-undoing to think that not facing the principle associated with that planet consciously will somehow make it take care of itself.