Hollow Man Suit
Start the Costume Party quest by purchasing the Cursed Skull from Murgo for five gold. When you examine the skull in your inventory, you are transported to a graveyard. Follow the golden trail to a large stone statue that identifies itself as a Cursed Knight in need of help. Follow the new golden trail to find a Hollow Man Suit in a sarcophagus. Equip it and continue down the path until you find a statue. Use the Bloodlust Roar expression in front of the statue to open the gate. Proceed through the gate.
Balverine Suit
Use your sword to cut through the bushes in front of you and continue down the path. Kill the Balverine that confronts you. A bit further down the path a new foe, the Poison Balverine, appears. Kill it, along with the others, to open the gate behind you. Go through the gate to get the Balverine Suit and then equip it. Follow the golden trail back to a stone jail cell. Use the Growl expression to unlock the cell. Equip the Hollow Man Suit and walk near the glowing wisps. Lead the wisps back to the Cursed Knight.
Hobbe Suit
Follow the new trail until you reach a locked gate. Put on the Balverine Suit and use the Growl expression to open the gate. Continue walking and kill the Hobbes that appear. Go through the door to the Mysterious Cave. Once inside, cut down the boards blocking your path. At the end of the path, pick up the Hobbe Suit. Put it on and walk up to the statue in the center of the cave. Lead the Hobbe that appears to the rocks blocking your path, and it destroys the rocks. Jump down to the lower ledge. Lead the backpack-wearing Hobbe to the boulder to destroy it. Lead the Hobbe on stilts across the poison pond to pull the lever, opening a door for you.
Final Battle
Exit the cave via the door and walk up the cell. With the Hobbe Suit on, use your Point and Laugh expression to unlock the door. As before, put on the Hollow Man Suit to get the wisps to follow you. Take them back to the Cursed Knight, who devours the wisps and turns into a necromancer. Use the Time Control spell to slow the necromancer down and then cast Raise Dead. The undead army you have raised will destroy the Hollow Men that the necromancer summons. Attack the necromancer with any offensive spell to damage and kill him. When the necromancer is dead, step on the teleporter to return to the docks of Bowerstone.