The term 'Royal Domain' can be broken down into two crossword solutions: REALM (5 letters) and EMPIRE (6 letters). A REALM is a kingdom or domain ruled by a monarch, while an EMPIRE is a large political unit with several territories or countries under the same ruler. Historically, empires have been ruled by an emperor or empress, while realms have been ruled by a king or queen. Empires are typically larger than realms, and often encompass multiple cultures and languages.