Mix cake according to manufacturer’s instructions. Measure out 3 pounds batter, deposit 1 pound into a sprayed and papered 8-inch cake pan. Repeat two times to make 3 cakes total. Bake at 350 ͦF until cake springs back lightly when touched. Let cool completely.
Fill and ice cake with purple buttercreme. Place Halloween sprinkles around the bottom of the cake. Using a large leaf tip, stripe piping bag with purple, black, and green buttercremes and reserve. Warm up flat icing and mix with neon green food coloring to desired hue. Pipe flat icing around edges of cake to make a drip design, then fill in on top. Let flat icing set up completely. Using reserved piping bag with leaf tip, pipe border on top of cake.
No dark Devil’s Food Cake Mix available in your area? No problem, just substitute Dawn Exceptional® Baker's Request™ Devil's Food Cake Mix (00495128).