The 8th house

The 8th house rules the base of the spine, the genital and the seat of mysticism or the kundalini chakra, the lower chakra. The 7th house ruling the spouse drains away the energy of the 8th house, because the spouse offers us unlimited sex life which drains away the vital source of energy which is seated within the 8th house. It is said that the 8th house rules mysticism. This is referring to the mystic processes of yoga such as Kundalini Yoga. Most of the Yoga systems of India, especially the serious mystic processes, all assume the position of brahmachari or celibacy because of the great need for the seminal energy regardless of the practitioners gender, in order to begin and sustain the mental concentration required for these yogic processes.
The 8th house also rules longevity and the 7th house which amongst other things governs our love life, drains away our vital energy decreasing our life span. This is the opinion of the Ayurvedic and other Vedic scriptures that deal with the energies within the body. This does not mean that Vedic wisdom is anti-sex life exactly, but there is a price for every action. If you want one thing, you have to give up those things opposed to it. For 8th house style Kundalini Yogic processes, retention of the sexual energy is essential.
The 8th house rules independent endeavor to achieve mystic power. It is 12th to the 9th house. The 9th house rules the receiving of power through the process of grace, revelation, or in other words, gifts from God. Therefore, the 9th house rules really very pure religion because of its basis being dependence upon the supreme power, whereas the 8th house rules our own individual, empirical endeavor to achieve mystic power through yoga and other difficult processes. So, since the 8th house rules the approach to mystic power which is opposed to simply receiving grace from God, it is, therefore, 12th from the 9th.
Also, on another level, the 9th house represents father. The 8th house, therefore, represents loss of father. Therefore, if we find the 9th lord in the 8th house in a chart, it is often found that the person lost their father.