Me, the Legitimate Heir: The Empress Wants Me to Marry into Another Kingdom?

Li Guanmin had spent eight years trapped, racking his brains for a way to escape. He never expected the Empress to send down an imperial edict ordering him to marry into a tribe on the grasslands. What... kind of move was that? After comparing things with the original story, he realized the plot had changed. The current empress, “Zhaoyue,” had been taken over by a “female lead” who held her fist high. Li Guanmin smiled. Truly, a thousand plans from a wise man are no match for one idea from a fool! Since that's how it is, then thank you. When I return that day, I'll leave you with your whole corpse. Far away on the grasslands, the ruler of the Anyan Kingdom was full of ambition and commanded a powerful army. He was wavering between rebellion and putting it off for now when he suddenly heard that the empress was sending a prince to marry into his kingdom... “Actually, my original surname was Liu. I have Han imperial blood in my veins. Now that my worthy son-in-law has been usurped by this demon empress, I must follow the will of Heaven, kill the demon empress, and secure the realm of Great Tang!” “Demon empress, prepare to die!” Years later, Li Guanmin gazed at the vast lands beneath his feet, all the way to the horizons touched by sun and moon, now the territory of Great Tang. He smiled and once again thanked the “Empress” he had killed with his own hands long ago.