A mutable grand cross occurs when four planets create 90-degree aspects in the mutable zodiac signs: Gemini, Virgo, Sagittarius, and Pisces. This planetary standoff creates a certain type of dynamic within the birth chart.
In astrology, a grand cross is when four planets are occupying each of the zodiac signs associated with one modality. For example, a fixed grand cross would mean that someone has four planets in fixed signs: one planet in Taurus, another in Leo, another in Scorpio, and a final one in Aquarius.
The grand cross, sometimes also referred to as a grand square, occurs when these four planets are 90 degrees apart, which also includes two oppositions with planets sitting 180 degrees apart. Every planet will be in the same modality, i.e., cardinal, fixed, or mutable, and each planet will show up in a different element: fire, earth, air, and water.
Mutable Grand Cross:
A mutable grand cross occurs when four planets are in the mutable signs of Gemini, Virgo, Sagittarius, and Pisces. If you have to have a grand cross in your birth chart, this formation at least allows for some room for negotiation between the four planets that are activated.
If you have a natal mutable grand cross, it can sometimes feel like every planet in your birth chart is trying to get their way but working at cross-purposes with different parts of your personality, wants, desires and goals. Each planet, sitting in a different element, has its own agenda it would like to enact.