King Boo

King Boo appeared in 2001 video game called Luigi's Mansion. King Boo is the leader of the Boos and ghosts, ruler of the Paranormal Dimension, the main antagonist of the Luigi's Mansion series, and the arch-enemy of Luigi. He is also an ally of Bowser, who has aided him in his various schemes. He is more than capable of devising and enacting villainous plans by himself, including his capture and imprisonment of Mario. Although not the biggest Boo named Boohemoth, King Boo has abilities that far surpass that of the average ghost; he wields a number of impressive magical abilities, including the ability to materialize objects. King Boo's magical power is directly proportional to the number of Boos in his vicinity.

King Boo's appearance has changed throughout his video game history. In his debut appearance in Luigi's Mansion, King Boo has dark red eyes, a blue tongue, two vampire-like fangs, a greenish complexion, and a ruby crown. In recent appearances, he resembles a white Boo with a golden, five-pointed crown, though he is noticeably larger. As well, the crown has a blue jewel on the front and four red jewels around the sides in every game except Mario Super Sluggers, where the colors are reversed. He first appeared in this form in Mario Kart: Double Dash!!, and it remains his current appearance to this day. However, his appearance in Luigi's Mansion: Dark Moon shows him with his original appearance, although he retains a full row of four teeth. He also has his eyes surrounded by a black shadow and has a more purple mouth and tongue, as well as his crown having a purple jewel. He has also lost his original green tint, now ranging from purplish to pure white. His new speech icon in the remake of Luigi's Mansion however, does have green shading.

Powers and Abilities
Besides possessing the abilities of other Boos, including the ability to teleport, King Boo has a numerous amount of other powers. Notably in Luigi's Mansion, King Boo's power increases when he is in the presence of other Boos. For example, King Boo has the power to blow Luigi to the Foyer when enough Boos are in the mansion. King Boo also has the power to materialize things, including pulling a highly detailed mansion out of the ghost dimension and creating lifelike paranormal replicas of some of Mario's enemies. He has shown the ability to create Boos or dimensions to battle in and even bubbles and blue fire, which he spits out of his mouth. King Boo is also shown to be able to regenerate from his crown in Super Princess Peach. He is shown to also have the power to grow in size as seen in Luigi's Mansion: Dark Moon.

In Luigi's Mansion: Dark Moon, King Boo exhibits new abilities such as being able to open paranormal portals (which lead to the ghost dimension), create traps such as sand patches, electrify the terrain to shock Luigi, and teach Boos how to create Spirit Balls. His new crown can also shoot an ectoplasmic laser that can shatter the Dark Moon or trap Toads within paintings. King Boo can create illusions, hence his title "The Master of Illusions." His power is also no longer reliant on the presence of other Boos, although it is stronger when there are other Boos in the vicinity.

King Boo appears with a rather high power stat in many of his spin-off appearances. This is most noticeable in the Mario Baseball series, where he is able to hit home runs with relative ease. His great strength is also shown in Luigi's Mansion: Dark Moon as he summons spike balls and makes them fall down, even the larger ones, simply by slamming the platform. King Boo also appears to be a good Alpine Skier, as he states that he is exceptional at that event, though this remains questionable due to his lack of skis (or legs for that matter).

In Mario & Luigi: Paper Jam, King Boo showed the ability to shape-shift, shown when he tries to trick Mario and Luigi by posing as Paper Mario, and later briefly transforming into Paper Peach and Paper Bowser. He also had the ability to spit blue fireballs.