Key to the Subconscious Mind
Neptune indicates the manner in which the individual's imagination and aesthetic and intuitive faculties work. Neptune rules the picture-making faculties of the mind If strongly featured, indicates a highly developed imagination with the capacity to pluck inspiration out of the air.
Neptune, the planet of deception and spiritual enlightenment, rules the oppressed and abandoned: the misfits of society. On a higher level he rules visionaries, and those who are glamorous and charismatic. Neptune represents spirituality, mysticism, and ideals.
Speaking personally, Neptune's house position and aspects with other planets in your chart will describe spirituality, abstract thinking, illusion, disillusionment, and areas of your life where things aren't always what they seem. Neptune rules derangement, guilt, persecution and describes the potential for experiences related to confinement, abandonment, and addiction or physical intolerance to drugs and alcohol.
In mythology, Neptune was a son of Saturn and brother to Jupiter and Pluto. Known as Poseidon ("tamer of horses and saviour of ships") to the ancient Greeks, he was Lord of the Sea and the god of horses. After the overthrow of Saturn, Jupiter became god of the heavens, Neptune god of the sea and Pluto god of the underworld. Despite his undeniable mythological credentials, some modern astrologers hold that the astrological influence of Neptune is feminine, presumably as he is often presented as an octave of Venus.
Neptune's role in society is often to cloud the issues, making things seem other than they are. Neptune is the master of disguise. Ruling oil, liquids, solvents (and makeup!), this mighty force usually operates beneath the surface, but can be brought into the forefront of consciousness when affected by significant transits from the visible planets – as it has been recently in the oil crisis and the floods, hurricanes and storms that have so grievously affected certain parts of the world.
Neptune, one of the outer, transpersonal planets, spends about thirteen years in each sign, taking around 164 years to move through all twelve signs. Since 164 years separate people born during its transit of one sign and those born when it returns, Neptune's significance in any sign is described as generational or historical.