The word "fiefdom" refers to a domain or territory controlled by a person who has power and authority over it. It can also describe a situation where someone has a strong influence or control over a specific area or group of people. Full definition
His vicious personal fiefdom of Candyland becomes a symbol for the sadism, oppression, theft of identity, false assertion of enduring superiority and the corruption of the human spirit that lie behind slavery. (theguardian.com)
And that's just as many new political fiefdoms for the Chicago Teachers Union to attempt to control with its robust war chest. (chicagotribune.com)