The 12th House represents the subconscious, seclusion, the intangible, intuition, institutions, karma. Pisces, Jupiter and Neptune are the natural rulers.
Your Secret Self: Illuminating the Mysteries of the Twelfth House by Tracy Marks
The Twelfth House: The Hidden Power in the Horoscope by Karen Hamaker-Zondag
Learn more about the 12th House with Steve Judd