The pokemon will be battling inside a large hall in a haunted mansion at midnight. Because the battle takes place inside, no weather effects will work here and SolarBeam cannot be used either. There is also no external water source, external rocks or external grass. In addition, all of the Rotom appliances can be found in the mansion, although because they are not in the hall, the command to possess an appliance costs 12 energy.
At the end of each round, one of the following will happen at random, with a 20% chance for each event:
- The bath in the upstairs bathroom will fall through the hall's ceiling and land in the middle of the hall. For the rest of the battle, there will be an external water source; however, a Frillish will use Scald on the first pokemon that uses a move that requires an external water source.
- This event cannot happen at the end of round 1 and it can only happen once in the entire battle. If this event is rolled at the end of round 1 or after it has already happened, nothing will happen.
- A Chandelure floating close to the ceiling will use Will-O-Wisp on all active pokemon, even those that are already burned or immune to burn.
- A Misdreavus will materialise behind one active pokemon (chosen at random with each active pokemon having an equal chance of being chosen) and shriek loudly before quickly floating away. That pokemon will be unable to do anything on its next action.
- A Haunter will emerge from one of the walls, use Lick on one active pokemon (chosen at random with each active pokemon having an equal chance of being chosen), and then float through another wall.
- One of the Rotom appliances (chosen at random with each appliance having an equal chance of being chosen) will be possessed by a Rotom, who will then enter the hall, use its new form's special move (Overheat, Hydro Pump, Leaf Storm, Air Slash or Blizzard) on all active pokemon, and then return the possessed appliance to its original location.
- If, when this event is rolled, the chosen appliance is already being possessed by a player-owned Rotom, nothing will happen.