According to Emperor Quon the Jade Jaguar once stole tresure from the Kingdom of Wei-Ling until their Royal Sorcerer was able to speak with him. They offered him ten thousand pieces of treasure if he promised to stay in his cave which he agreed to. However he is known to be very protective of his treasure and traps anyone who tries to steal it.
When James and Jin found the map to his cave they went after the treasure only to get caught in his trap and the same went for Roland and Quon. Sofia, Amber and Jun were able to avoid his trap and Sofia tricked the Jaguar into getting stuck in the secret passage they came through. Sofia was able to reason with the Jade Jaguar to let their families go and promised to leave his treasure alone. He allowed Sofia's friends and family to leave his cave without any harm and remained with his treasure.
Technically, jaguars live in South and Central America. Since Wei-Ling is set in China, there should have been a native feline that was guarding the treasure, such as a leopard or snow leopard.