Melt the Mixture: In a large pot over medium heat, melt 3 tablespoons of butter. Stir in 10 ounces of marshmallows until melted and smooth, about 3-5 minutes.

Combine Rice Krispies: Fold in 6 cups of Rice Krispies cereal into the melted marshmallow mixture, ensure all are well coated, about 2 minutes.

Shape the Treats: Grease a 9x13-inch baking dish, press the mixture into an even layer using wax paper or greased hands. Let set for at least 30 minutes.

Cut and Shape: Once set, cut the treats into desired shapes like squares or spooky monsters, about 5-10 minutes.

Melt the Candy Coating: Melt candy melts in a microwave-safe bowl in 30-second intervals, stirring until smooth, about 1-2 minutes.

Decorate the Treats: Dip shapes in melted candy coating, add sprinkles or candy eyeballs while still wet. Let sit on parchment-lined baking sheet.

Set and Serve: Allow decorated treats to sit until candy coating hardens, about 15-20 minutes. Optionally, sprinkle edible glitter before serving.