According to legend, a long time ago, the Black Mountain in the northeast of Chengde was called Motianling, and the terrain here was dangerous, making it difficult for anyone to capture it. The west side of Motianling was cliffs, and the east side was connected to the mountains. Only the Longtan Valley in the south could be reached by mountain road.

In the battle against the Xiongnu at Mulan, the vanguard officer of the Xiongnu, Youxian King, lived here. The Xiongnu soldiers will defend Nanshankou. As long as there are soldiers and horses attacking the mountain, rolling wood and punching stones will fight down together, and there will be no one who will not be beaten back.

It is said that Hua Mulan swept the north and came here, but she could not attack several times in a row, so she had to station the soldiers and horses first. The place where the soldiers and horses were stationed was now Hua Mulan City. At that time, Hua Mulan had been in the army for more than ten years, and she missed her parents and the villagers in her heart. She hated being able to step on the Ferris Ridge with one foot and return to the court. She sat in the big tent and thought of a plan, but she couldn't think of a good way.

One day, Hua Mulan led the soldiers to Erlong Mountain opposite the Ferris Ridge to observe the terrain. When they saw a group of sheep jumping up and down the steep mountain, they couldn't help but sigh, "If only people had the ability to climb mountains like sheep!"

That night, she took the soldiers to check the sentry with lanterns, and suddenly there was a sheep cry of "baa-", which startled her. She suddenly thought: Why don't I use sheep lanterns to break the sky ridge!

The next day, she sent her soldiers around to buy sheep and built a sheep castle on the top of Erlong Mountain, which is now Locking Sheep City. She sent paperworkers to paste lanterns day and night. She also visited local mountain people nearby and found a way to climb the mountain.

On a dark night, Hua Mulan asked the soldiers to hang lanterns on the horns of each sheep and drive them into Longtanwa. The flock of sheep ran all over the mountains to the Motianling. When the Xiongnu guards saw it, they thought it was the men and horses of Hua Mulan attacking the mountain, so they set off the rolling wood and beating stones. When the sheep saw the wood and stones rolling, some fled to the rocks in fear, and some ran up the steep slope. This scared the right wise king! How could they climb the dangerous stone? Could it be the heavenly soldiers? The Xiongnu soldiers did not know the truth and were in a mess; Hua Mulan took the opportunity to attack from the path and killed more than half of the Xiongnu soldiers. The right wise king led the remnant and ran back to the northern country in one go, and never dared to invade again.

Hua Mulan, with her clever intelligence and brave fighting spirit, captured the Fantian Ridge, distributed the things robbed by the Xiongnu to the people, and the class teacher returned to the dynasty.