Pluto in 8th House synastry relationships are based on mutual enthusiasm for spiritual and religious teachings, research, military activities, and those related to law and order. The “Plutonian” personality helps the personality of the Eighth House to penetrate deeper into the spheres of the spiritual and mystical, as well as to look at reality more meaningfully and intelligently.
In a negative scenario of Pluto in Eighth House synastry, the partners experience a noticeable emotional decline in each other’s presence, fears, and anxiety. In a positive scenario (requiring sufficient psychological maturity), the partners are actively engaged in parapsychology, which significantly helps in their constructive activities in all life spheres.
from F. Sakoyan, L. Ecker
Pluto in 8th House Synastry Explained
Pluto in 8th House synastry is not the easiest aspect to build relationships, even though Pluto is the ruler here. Nevertheless, with its correct understanding, this aspect gives a lot to both partners, at least if they are able to open up to the idea of spiritual purification and sacrifice as something positive or at least necessary.
But, of course, at first, the behavior of a Pluto in Eighth House synastry partner in your crisis or a psychologically difficult situation may not particularly please you. The partner will likely try to explain that you have only half of what you really could have, especially if you take into account (1) the mistakes that you have committed in your lifetime, and (2) the vices that you have not yet overcome. Moreover, the partner will not mind listing all those mistakes and vices, which may seem unfair and cruel to you; but often their words will contain a lot of truth, so you better not be offended and try to perceive it.
Of course, at a low evolutionary level of Pluto, the partner will seem impossibly rude and tactless; but your harsh reactions, especially in marginal states of distress, will have a strong impact on this partner, which he or she most likely will not expect, assuming their complete control over you. Nevertheless, your Pluto in 8th House synastry partner’s losses as a result of your interactions may turn out to be fatal and irrevocable, and here the roles may change, so you will have to become their trusted psychologist and savior.
In order for your relationship with a Pluto on 8th House synastry partner to become constructive, you must be subtle and psychologically literate, since this aspect affects very sensitive programs of the subconscious (and life circumstances) of you both. The good news is that the positive effects of a mutual spiritual cleansing will surpass any expectations, elevating you both to a formerly unknown state of silent internal power that easily translates into various forms of external control over other people and circumstances at your will.
from A. Podvodny