In "Empress Ki," the battle rages on between the Empress Dowager, played by Baek Jin Hee, and El Temur, played by Jeon Guk Hwan, and the pawn in the middle of all this intrigue is a royal concubine.

While El Temur is pulling the strings of the puppet emperor, played by Ji Chang Wook, the Empress Dowager hopes for a day when that influence ends.

The only way to diminish his power is to ensure that the emperor and his wife, the daughter of El Temur don't have any offspring that might potentially inherit the throne. The Empress Dowager does everything she can to curb his power, including giving the Empress incense that will potentially render her sterile, and introducing a concubine to provide the emperor with another heir.

But what exactly is a concubine?

It's a relationship that has existed since ancient times and was practiced by the royal houses of both Korea and China. A concubine is a woman who has a relationship akin to marriage, except that it's not legal. Generally women did not choose to be concubines but were enslaved or given as a tribute, although some women did seek to become concubines to improve their status. While the concubine is not legally married, any child she has with a ruler can inherit the throne and ensure her future. Concubines also insured that a ruler would have heirs to spare if he could not conceive with his spouse.

But this system of inheritance naturally led to conflicts within the palace, jealousies between wives and concubines and between their offspring.

A good example of the kind of trouble this can cause was the story of Jang Ok Jung, who rose from the ranks of concubine to depose Queen Inhyun, become Queen Consort, and then ultimately was deposed.

When rulers had many concubines, complex systems arose to designate their status. Royal Noble Consort was the title of royal concubines to kings during several periods of Korean history and they were divided into several ranks. The upper four ranks were considered part of the royal family.

The Chinese emperor had an empress, royal consorts and concubines, with heirs ranked according to their mother's status. At times there was more than one Empress. Although "Empress Ki" is historical fiction, it is based on the story of a real-life Korean concubine that became an empress of the Yuan Dynasty in China. She was delivered to China as a tribute and probably did not really fight her way there with a sword, but she did have to battle through court intrigues to rise to the rank of empress.

Will Ha Ji Won's character become a concubine before she rules? If she does, she will become one worthy of ruling a country.