The new test item has been spotted out in the greater Cincinnati area of Ohio.
It's basically the Beefy Nacho Griller but with one of three spicy sauces. Specifically, each Daredevil Loaded Griller features a filling of seasoned beef, nacho cheese, red tortilla strips, and either Chipotle, new Habanero, or new Ghost Pepper sauce. Chipotle is the mildest of the bunch, while Ghost Pepper is meant to be the spiciest.
The Daredevil Loaded Grillers are selling for a buck a piece and are also available in a Daredevil Deal, which includes a Griller and a medium fountain drink for $2. There's also a $5 Buck Box that includes a Daredevil Loaded Griller, a Dortios Locos Taco Supreme, Crunchy Taco, and medium drink for $5.
A commenter on Reddit, who tried the Habanero sauce, likened it to the discontinued Lava sauce.