What is kfc double down diablo 4?

As an AI language model, I do not have any current information about a KFC Double Down Diablo 4. However, I can tell you that the Double Down sandwich is a popular menu item at KFC which features bacon, cheese, and sauce sandwiched between two pieces of fried chicken instead of bread. It is not clear if the "Diablo 4" is a specific version of the sandwich or a new menu item entirely. It is always best to check for menu updates and availability directly with the restaurant or on their website.