Collect four coloured keys from the penthouse rooms, disable Hellen Gravely’s laser arena and rescue Mario. Complete the hotel’s optional collection before following Mario into the final rooftop sequence.
Lounge and corridor
Stand both characters on the lounge coffee tables for green. Send Gooigi through the upper-left pipe and down behind the elevator pillar for purple. Vacuum the screen with both characters to open the way onward. In the southwest corridor, rotate the sculpture to match the Boo shadow, then Luigi’s outline, for white.
Library — yellow key
Use Burst to stir dust and expose otherwise invisible laser beams. Work through the lower library route and disable the hazards before taking the key. Carry the solid brown book from the lower-left room to the empty slot on the upper-right shelf for the red gem.
Drawing Room — green key
Reveal the Drawing Room door with Dark-Light. Put one character by the rear fireplace and have the other turn the windmill painting on the left. Rotate until the power-panel compartment faces the fireplace, then enter it from behind and pull its switch to disable the lasers. Rotate again to expose the green-key compartment and collect the key safely.
Master Bedroom — purple key
Pull the right mannequin with Suction Shot to turn the room into a seesaw. Use Gooigi for the climb, shifting sides in short steps to avoid tipping the platform too far. Stir dust to reveal lasers. The highest barred alcove contains the yellow gem; collect the purple key along the bedroom route.
Master Bathroom — blue key
Turn off the shower and use Gooigi’s lower pipes for the blue gem. Clear the sauna hazards to obtain the blue key. Check the sauna’s hidden gold ghosts before leaving if completing the Master Bathroom achievement.
Four-key door and final ghost groups
Defeat the corridor ambushes and place each key in its matching colour lock. Make a collection check before entering Hellen’s office. This is the last regular floor, and there is no Boo to capture on 15F.
Hellen Gravely — red laser
Use Burst to jump the low red beam and move around the other patterns. Open the floor access for Gooigi and send him below the arena. Luigi must remain safe above while the duplicate works on the coloured barrier switches.
Hellen Gravely — coloured barriers
Turn the underground obstacles and reach the switches matching the coloured laser walls. Some switches require Suction Shot. Disable enough barriers to give Luigi a clear route, switch back up and dodge Hellen’s mirror attack. When the mirror sticks after her strike, flash her and capture her. Repeat as barriers are reactivated and the arena becomes less forgiving.
Rescue Mario and prepare for the roof
Use Dark-Light on Mario’s painting. Before following him past the office into the rooftop route, return for any missing gems, Boos, money or achievements. The final battle has no free exploration afterward; replaying the hotel uses an earlier save checkpoint. Follow the separate King Boo guide when ready.
Gems and floor completion
Use the six-colour list to finish this floor. Check the required return visit before trying a route that needs Gooigi, Super Suction or the later Toad mission.
- All six gems — 15F — Master Suite
- Boo locations and capture method
- Floor achievements and full checklist
Continue the walkthrough
Next: