I find that these houses are often grouped together within the context of planetary interpretation. Though, there are nuanced differences between them. They are talked about in such strong tandem that the 8th and 12th house appear to offer us the same things: hardship, challenge, spirituality, meditation, death, loss, the occult. All things immaterial, woo-woo, psychic or magical. The 8th and 12th trine one another, but then so does the 4th, yet the 4th is largely left out of the conversation. More on that another day (sorry 4th). Below is what I find to be the difference between the 8th and the 12th, both as a personal holder of planets here, and from client work.