Haunted Houses in Festival Plaza are basically mini adventures a player can send their Pokemon on in order to receive items for the price of 10 Festival Coins. The items you will receive are at random; however, the higher thee rank of the Haunted House, the more likely you will be to get better prizes.
Possible Prizes
Ghost's Den: Sacred Ash, Bottle Cap, PP Up, Heart Scale, Patterned Poke Bean, Festival Ticket, HP Up, Protein, Full Heal, Hard Stone
Trick Room: Sacred Ash, Bottle Cap, Max Revive, Heart Scale, Patterned Poke Bean, Festival Ticket, Iron, Carbos, Hyper Potion, Hard Stone
Confuse Ray: Sacred Ash, Bottle Cap, Max Elixir, Heart Scale, Patterned Poke Bean, Festival Ticket, Calcium, Zinc, Ultra Ball, Hard Stone