T-Squares
The T-Squares are "drivers" to accomplish something. Their meaning, in a general sense, derives from the three aspects involved: 1) the opposition, 2) the opening square, and 3) the closing square. Once you understand these dynamics the rest is easy.
The opposition (Neptune opp. Asc.) is confrontation, projection, partnering and reaching out -- a conflicting set of keywords if there ever were any. The polarity recognizes "self" and "not self". We know ourselves, supposedly, but often don't know others. We can project qualities upon them which we are looking for -- but they may not accept them or act accordingly. This leads, often, to confrontation -- we often fight that which we don't understand. On the other hand, we may be intrigued by the "not self" or the "other" and wish to establish a rapport or partnership of some kind and depth. This is what polarity is all about, a cyclic approach to things. For you, Neptune opposite the Asc. angle can involve "fear" of the unknown, or intrigue with "entertainment, illusion or showmanship, etc.", or a capacity for seeing others in an idealistic light, or trying to form a partnership with a dream or with an ideal (religion, phillosophy, social cause, etc.). In fact, you may do all of those things to a greater or lesser extent.
Remember, when we have options, we tend to exercise them all.
Neptune forms a square to your tenth house planets. We don't know which they are but we can assume they might be any planet except Pluto. If so, they all move faster than Neptune so Neptune will be the anchor point and those planets will be "opening" squares. This suggests that they will offer challenges to how Neptune expresses itself in terms of partners and joint efforts. Sun, for example, would continually push for Neptune to recognize facts and truth -- goals would have to recognize what was showmanship and what was just hope, smoke and mirrors as wishes.
The 10th house stellium would be a "closing" square to the ASC angle, picking up the 10th house meaning. They would be trying to establish and be recognized for their accomplishments. They would be a source of visible pride and effort and their success in expressing themselves would have a direct effect on your personality and well-being. This, again, supports the 7th house Neptune placement -- you need to focus on what/who you are and not on who you appear to others or on what others appear to be for you. Be centered, be yourself, then relate to others from that context.
Dave.