The Great Queen Seondeok(2009)

Original title: 선덕여왕

A royal prophecy warns that the birth of twins will end the male line of succession. To protect the kingdom, one twin sister is exiled to a distant desert, growing up unaware of her royal heritage. Years later, she returns disguised as a man, joining an elite order of warriors. Alongside loyal allies and an outcast warrior, she fights to reclaim her identity and overthrow a corrupt rival faction threatening the throne.