Fiefdom

noun

1. The estate controlled by a feudal lord; a fief.

   "The duke's fiefdom had been greatly expanded as a reward for his dutiful military service on behalf of the king."

2. (by extension) Any organization in the control of a dominant individual.

   "Most of our company's computers are standardized, but the IT director allows the employees in his own little fiefdom to specify their own machines."