The king has a constant pain in his side as most Rulers do, a claimant to his throne, Former Queen Christina. He is based on a real person who ruled Sweden from 1654-1660. He seems to be a humble king as he leaves all cities and fortresses to his vassals and gives himself a mere castle, despite having the power to have the capital city like most rulers would do, especially in the earlier games.
Although his name was King Charles X Gustav of Sweden, he was actually the fourth King Charles.
Johann Koster, a doctor for the king, mistook his pneumonia contracted by traveling throughout the kingdom with a cold for scorbut and dyspepsia. The pneumonia then evolved into a sepsis, which caused his death on February 13, 1660, at the age of 37.