Alandra Data Repository
As mentioned, the distinctions are physical as well as social. Nobility is established by birth, but a commoner can be promoted in his or her social status.
Nobles are taller and more muscular in appearance than average. In Vincetti, nobles have violet skin, whereas commoners have deep purple skin. (This distinction does not exist between Alandran subjects.)
Nobles are much stronger than commoners, in several ways. Physical strength is increased, often by tenfold or more. Nobles are also much faster than commoners.
The most obvious, and in a fight, useful, way that nobles differ is their resistance to blaster fire. Energy weapons are almost useless on members of the nobility, as energy weapons have little to no effect on a noble.
Nobles fill all high-ranking military positions. Also, in Alandra, only nobility can partake of the Wine of the Sacrament. Vincetti have a similar drink available only to nobles, but do not have the rituals associated with it.
On the rare occasion when a commoner is promoted to the nobility, the promotion happens on the Day of Mourning, and the commoner can then drink the Wine of the Sacrament. Only then are they considered a noble.
Such promoted nobles are neither as strong or tall as natural-born nobles. Often, a natural-born noble will not consider a promoted noble to be his social equal. This has created an un-official third caste.