Every temple complex had its adyton — the innermost chamber where only initiates entered, and no one returned unchanged. The Eighth House is that chamber: Hades' realm in the architecture of the chart, governing what is shared so deeply it cannot be untangled — sexual intimacy, joint finances, inheritance, debts, and the psyche's basement where the unprocessed waits. It is also the house of death in its largest sense: every ending that makes a beginning possible.
Planets here describe your relationship with depth itself — how you merge, what you fear losing, how you handle other people's resources and other people's darkness, and the transformations your life will insist upon. Eighth House people are the ones others trust with the unspeakable; they have usually paid for that trust in descents of their own.
Its teaching is the underworld's oldest law: what you bury alive stays alive, and what you grieve properly becomes wealth. Persephone returned from Hades carrying spring. The Eighth House asks you to go down willingly — because everything in you that is unkillable is only discovered there.