Three Kingdoms: Start at Yanmen Pass and Eat Sand

He was the legitimate son of the Yang family in Hongnong. He was supposed to go to Luoyang to enjoy the blessings, but he was thrown into Yanmen Pass and gnawed on the sand for ten years. Bind to the border city building system, each time you defend against an alien invasion, you will unlock a black city defense technology. But as soon as the granary was replenished, the imperial envoy rushed to deliver a message - asking me to commit suicide in the name of disloyalty.