Mercury

Budha is the discriminating intellect — the faculty that tells one thing from another, counts, writes and trades. Where the Moon receives, Mercury analyses.

Its nature is conditional in a way no other graha’s is: Mercury takes on the character of whatever it sits with. Alone it is benefic; with a malefic it becomes one. This is why a reading that names Mercury’s associations is far more useful than one that names only its house.

It is the only graha both ruling and exalted in the same sign, Virgo, which makes that placement unusually pure.