Neptune in 10th House synastry relationships are characterized by their fragility, instability, and ambiguity, especially in such areas of joint life activity as business, finance, and politics.
In a positive scenario, the “Neptunian” personality helps the development of the career of the Tenth House person thanks to his intuitive-creative imagination, especially in the creative spheres of active life. The partners effectively collaborate in areas requiring a creative approach, including culture, religion, spiritual and higher education, charitable and humanitarian activities.
In a negative scenario, mutual understanding and harmony are violated, which leads to conflicts, unreliable partnership, and disagreements in general which, of course, does not result in a positive and constructive relationship.
from F. Sakoyan, L. Ecker
Neptune in 10th House Synastry Explained
In a harmonious version of Neptune in 10th House synastry, discussing the situations of your choice and professional advancement can lead the partner to an almost ecstatic state. But it will be almost impossible for you to wait for sober advice and opinions. In difficult cases for you, especially if you ask for help, the partner may really want to help you, otherwise he will be feeling guilty and inclined to either shove that guilt into the subconscious, or project it onto you. The partner’s usual reproach may sound something like this: “When you have difficulties and need to look for ways to get out of the current situation, you state it so vaguely that you do not understand anything, or you understand it in a wrong way.”
In turn, you can notice that the appearance of a Neptune in 10th House synastry partner often messes up your plans and relationships with superiors and subordinates alike. In matters of your practical ethics, this partner may seem capable of getting entangled in the simplest problems and confusing you, which is quite dangerous for you both since at the same time even the most obvious unseemly actions are somehow blurred and begin to look almost decent.
It may seem to your Neptune in Tenth House synastry partner that you deliberately fool him or her with your problems, distorting the true state of affairs and hiding the most important details – and to some extent they will be right. At least reaching an exact mutual understanding will be difficult for you two for a long time. But at a high level of spiritual development, the partner will help you rise to the level of distinguished religious ethics and understand what the will of God is in the specific case of you making a particular choice. However, this requires working out not only the partner’s Neptune and your Tenth House but your whole synastry chart, in particular, the Fourth House (religious views on life in general).
from A. Podvodny