Dark Boo

Dark Boos are purple, art-loving Boos that appear in Paper Mario: The Thousand-Year Door and Super Paper Mario. They may be found only in the hidden spot of the Poshley Sanctum and also in the Pit of 100 Trials. Dark Boos are more powerful than their white brethren.

Dark Boos later appeared in Mario & Luigi: Partners in Time in the Gritzy Caves area, it is a faster and stronger type from a counterpart of a Boo. Dark Boos have similar attack movements as Boos. If a Dark Boo opens up its right eye, it means it's going to attack Mario or Baby Mario by appearing behind Mario or Baby and ramming them. If a Dark Boo opens up its left eye, it means it's going to attack Luigi or Baby Luigi by appearing behind Luigi or Baby Luigi and ramming them. Additionally, if one of the Mario Bros. is attacked, the Dark Boo steals either a normal Item or a Bros. Item. The Mario Bros. have to be quick to get those items back by quickly defeating them before they run away.

Dark Boos resemble Pink Boos from Super Mario Sunshine.

Trivia
It is the only "Dark" enemy in Super Paper Mario that isn't a silhouette. The silhouette form of a Boo is called the Dark Dark Boo.