Part one of this post covered how aspects can alter a planet’s expression.
Another factor that can alter planetary expression is a natal stellium, or tightly knit group of four or more planets. They are often conjunct one another (within 10º), but multiple planets in one sign/house can activate each other like dominos, regardless of proximity. This area of the chart can become like a black hole, skewing the rest of the chart’s energy.
For example, an individual with Virgo Sun and Capricorn Moon is a would-be earthy type. However, this person has a closely conjunct Libra stellium of five planets: Mercury, Venus, Mars, Pluto, and Uranus. Libra becomes the focal point of her chart, despite the fact that her Sun, Moon, and Ascendant are not involved. When she reads the Libra traits and horoscope, they seem to more accurately depict her than her Sun sign of Virgo.
Individuals with stelliums come across as very intense, but paradoxically are oblivious to it, due to the subjectivity that comes with this placement. A stellium-native assumes that inside, everyone else feels the same way that they do! For example, an individual with Sun, Mercury, Venus, and Mars in Leo has a lot of energy tied up in ego expression. He comes across as proud and dramatic to other people, but is unaware of these character traits because he assumes all people feel that strongly about themselves!
Something that helps balance a stellium is a natal opposition. The Libra stellium woman would be helped by an Aries planet to make her more decisive, and our Leo stellium man would do well with a detached Aquarius planet. Oppositions in general bring some needed objectivity to a native, regardless of whether it involves the stellium. But if these aren’t available in the natal chart, the person may seek out these opposing qualities in others to bring balance to their own life. A mate with personal planets that oppose your stellium can bring a lot of much needed perspective to your life!
Transits and progressions that affect one planet in the stellium will often activate the rest, which is why so much energy gets sucked into this part of the natal chart. They activate each other like dominos, and then each house that is ruled by the planets is affected, etc. So a large portion of your life can be affected by a single transit or progression, if you have a natal stellium!