Principality

n. territory ruled by a prince

A principality (or princedom) is a monarchical feudatory or sovereign state, ruled or reigned over by a monarch with the title of prince or princess, or (in the widest sense) a monarch with another title within the generic use of the term prince.
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Noun
1. territory ruled by a prince
(synonym) princedom
(hypernym) domain, demesne, land
(hyponym) Wales, Cymru, Cambria

(n.)
The territory or jurisdiction of a prince; or the country which gives title to a prince; as, the principality of Wales.
  

(n.)
Sovereignty; supreme power; hence, superiority; predominance; high, or the highest, station.
  

(n.)
A prince; one invested with sovereignty.
  

In an SCA context, a subdivision of a kingdom either for the administrative convenience or instituted with the development of a new kingdom in mind.