In astrological tradition, the Neptune governs imagination, dreams, and the dissolving of boundaries, while Scorpio is a water sign read as intense, private, perceptive, and all-or-nothing.
So Neptune in Scorpio is often read as a placement where where intuition, art, and longing tend to gather takes on a intense, private quality. Tradition holds that someone with this placement tends to dreams and idealizes in a way that feels perceptive — coloured by the water-sign temperament of Scorpio rather than by any single rule.
None of this is a prediction or a fixed trait. These are tendencies astrologers have long associated with Neptune in Scorpio, and how they actually show up depends on the rest of the chart — the houses, the aspects, and the other placements that this guide cannot see.
A general guide to astrological tradition — tendencies, not predictions. It describes the placement in the abstract and is not about any specific person.