Li Shimin, You Want Me to Fight the Monkey King?

The protagonist Lin Che, a top history student from the 21st century, traveled to the early Tang Dynasty and became Li Jiancheng's unknown illegitimate son, who was exiled to the northwest. With knowledge that was ahead of his time and ruthless methods, in ten years, he became the king of Northwest Liang with hundreds of thousands of troops and a separate kingdom. He originally thought that his biggest enemy would be the talented and strategic Li Shimin, Emperor Taizong of the Tang Dynasty, known as the "Khan of Heaven". However, when his cavalry entered the Central Plains for the first time and were about to approach Chang'an, an iron rod fell from the sky and smashed his most elite vanguard unit. A monkey wearing chain-locked gold armor, a purple gold crown with phoenix wings, and a wishful golden hoop stood in front of Chang'an City. "You said that Li Shimin sitting on the dragon throne... He has the Monkey King as his bodyguard?!" This Tang Dynasty has a mythological background? Why didn't you tell me earlier!