To make towers which will be inserted into cakes more stable, attach Plastic Dowel Rods to bottom of towers as follows: For 2 small towers, cut 2 and 2 1/2 in. dowel rods; for 3 medium and 1 small towers, cut dowel rods 1 in. shorter than height of cake. Stand towers upside down; attach cut dowel rod to base with melted candy. Refrigerate until firm.
Tint 8 oz. fondant yellow, 16 oz. violet, 1 oz. black, reserve 1 oz. white, tint remainder gray.
Bake and cool 2-layer 10 in. rounds 2 1/2 in. high; trim for 5 in. high cake. Bake and cool 2-layer 6 in. rounds for 4 in. high cake.
Prepare cakes for Stacked Construction; position 6 in. cake 1/2 in. toward back of 10 in. cake to allow for main roof. Using smallest square Cut-Out, imprint bricks on cake sides.
Make ghosts and bats. Roll out white and black fondant, 1/8 in. thick. Using Halloween Mini Cutters, cut approximately 5 ghosts, flip over cutter and cut 5 more ghosts; cut 4-5 bats. Let dry on cornstarch-dusted board. In royal icing, pipe tip 2 dot eyes and mouth on ghosts.
Make fondant windows for towers. Trace patterns of windows from towers and main roof. Roll out yellow fondant 1/8 in. thick. Cut out tower windows using patterns. Draw lattice design on windows using FoodWriter. For windowsills, roll violet fondant into thin logs and attach with piping gel. Prepare towers. Roll out gray fondant 1/8 in. thick and cover turret towers, securing with damp brush. Imprint bricks with smallest square Cut-Out. Using violet fondant rolled 1/8 in. thick, cut 4 in. circles for the small towers and 6 in. circles for medium and large towers. Use the wide end of tip 125 to cut a hole in the center of circles for small and medium towers. Use the wide end of tip 1A to cut a hole in center of circles for large towers. Thread circles over the towers; attach with a damp brush. Shape and trim notches on top edge for battlements. Roll out gray fondant 1/8 in. thick and use 3 in. round cookie cutter to cut a circle of fondant for each tower. Dampen and press inside towers. Attach windows to towers with damp brush. Prepare main roof.
Cover front of roof with gray fondant, secure with damp brush and trim. Cover window with fondant and decorate as for tower. For rooftop, roll out black fondant 1/8 in. thick; cut a 14 x 3 in. strip. Attach to roof with damp brush; trim. Using knife, mark sections 3/4 in. wide on roof, then score to resemble wood grain. Using royal icing and tip 3, add scallops on eaves (smooth with finger dipped in cornstarch).
Prepare door. Roll out gray fondant 1/8 in. thick, cut using door in set as pattern. Mark slats using ruler. Attach to door from set using piping gel. Pipe tip 2 outline door pulls.
Attach icing decorations around castle with royal icing. Tint coconut; cover board with coconut. Attach ghosts and bats to castle with melted candy.