Roman numeral code: iii
Scale notes: 3, 5, 7
Attributes: "far away", mysterious
3's essence is much different from that of 6 or 2. It seems remote and elusive. These qualities and its great harmonic 'distance' from 1 accounts for its rarity.
The 3 chord is plaintive, with a deep sense of longing. 3 is the most subtle of the harmonies, yet it can evoke sadness or mystery much better than 6 or 2.
The presence of scale note 7 is mainly what gives 3 its unique qualities. Because of its distance from 1 harmonically, 3 often returns to 1 in three steps: to 4 or 2, then to 5, then 1.