L5R LCG: Children of the Empire Exp. - Rules of Play says:
Children of the Empire is a premium expansion for Legend of the Five Rings: The Card Game, with this being a new level of product that features 234 cards (three copies each of 76 cards and one copy each of six cards), a number comparable to the Legend of the Five Rings: The Card Game Core Set. Unlike previous expansions, premium expansions are not tied to a specific clan, nor do they form part of a cycle; instead, these expansions focus on developing specific themes and mechanisms, rewarding every clan with a wealth of new cards in a single expansion!