Mules

Mules are a race of animals that inhabit Hidden Kingdom. They reside at Mule Castle, under the leadership of Mule King.

History
At some point the mules began to antagonize the local human population. First Squad stepped in to stop them, and were challenged to a competition of eating chili peppers.

Abilities
The mules are relatively strong, as shown by their ability to pull heavy plows. They are capable of powerful kicks, and seem to be resistant to the spiciness of chili peppers.

Trivia

 * Real-world mules are the offspring of a horse and a donkey, and are sterile. It is unclear if this is true for Hidden Kingdom's mules. There share this distinction with ligers, which are the offspring of a tiger and a lion.
 * The mules seem to be loosely inspired by Mexican culture. Mule King also has a faint Mexican accent.