Place the black beans in a mixing bowl and mash them lightly with a fork. Stir in the cumin, chili powder, and salt until evenly combined.
Use a bat-shaped cookie cutter to cut four bat shapes from four of the tortillas. Leave the remaining four tortillas whole to serve as bases.
Lay the four whole tortillas on a work surface. Spread the black bean mixture evenly over each one, then sprinkle the shredded cheddar cheese on top.
Place a bat-shaped tortilla piece on each prepared base and press down gently so the layers stick together.
Heat the olive oil in a large skillet over medium heat. Cook each quesadilla for 2 to 3 minutes per side until the tortilla is golden and the cheese has melted.
Transfer the cooked quesadillas to a cutting board. Serve with sour cream and salsa on the side.