Spirit Ball

Spirit Balls are ghosts that appear in Luigi's Mansion: Dark Moon and Luigi's Mansion 3 that were given to Boos from King Boo's power-enhancing bejeweled crown. Their appearance is based on either the  or the. After Luigi uses the Dark-Light Device on an invisible object to reveal its presence, Spirit Balls fly out, and Luigi must use his Poltergust 5000 or Poltergust G-00 to suck them up in order to make the object visible. If he does not suck the Spirit Balls in a certain amount of time, they go back to the object and turn it invisible again. Spirit Balls can hurt Luigi if he touches them, dealing 5 HP of damage.

In Luigi's Mansion: Dark Moon, in a mission in Gloomy Manor, a Boo is seen producing some Spirit Balls. Unlike other ghosts, they cannot be sent to the Vault and do not appear in the ScareScraper; invisible objects simply get revealed without needing to suck them up.