Yelps's chest is the storage box used by the goblin Yelps to hold his wealth. It is surrounded by Yelps's leftover spin tickets. Attempting to open it before the player has defeated Yelps prompts the message: "Looks like it's full of treasure, but Yelps wouldn't like you touching it."
The chest is located in the northern tent of the goblin camp and claiming Yelps's very own cash bag is a requirement for the master quest cape. The ticket is not a requirement for the master quest cape.