Dark Fawful is the revamped version of Fawful and the semifinal boss of Mario & Luigi: Bowser's Inside Story. In this form, Fawful has greater powers and an altered appearance, featuring red glasses, a cloak that resembles the one worn by his old mistress Cackletta, and his Vacuum Helmet that seemingly has a life of its own.
 Mario and Luigi: Bowser's Inside Story
Fawful transforms into Dark Fawful after stealing the Dark Star and absorbing some of its power, which increases his own powers. After Bowser defeats Super Peach's Castle, Fawful quickly engages him in battle, which takes place in the Conference Hall, the same area Mario and Luigi fought Bowser during the first tutorial battle.
Dark Fawful's attacks vary slightly depending both on whether or not Fawful has been substantially damaged and on whether his headgear is still present. Fawful's first attack is usually having his headgear grab the chandelier and swing Fawful at Bowser: the attack can be countered by punching Fawful, but punching him several times will cause Fawful to swing back behind Bowser in an attempt to ram him, forcing Bowser to duck. Two of Fawful's attacks involve him detaching himself from his headgear (assuming it is still intact). The first of these attacks involves Fawful pulling out his ray gun and firing eight stars that proceed to orbit around the screen: one will be large and pink initially, and Bowser must punch that star to blow all the others up and avoid taking damage and possibly being flipped over. The second attack Fawful performs while detached from his headgear involves Fawful flying to the top of the screen and setting up four portals - one each on Fawful's left and right, one above Bowser, and another next to Bowser. Fawful will then proceed to shoot energy orbs through the portals: if he shoots an orb through the portal on his left Bowser will have to duck, while Bowser will have to punch the offending ball of dark energy if Fawful shoots it through the portal on his right. All of these orbs can lower Bowser's defense if they hit him. The headgear will move Fawful out of the way of Bowser's punch and fire attacks and will regularly heal Fawful for 300 HP until it detaches itself from Fawful, so Bowser should wait until it does and then inhale the headgear to let the Bros. deal with it. Note that Bowser can also forcibly remove the headgear early by targeting it with a sufficiently strong special attack.
After his headgear is destroyed and/or he starts taking a substantial amount of damage , Fawful becomes much more aggressive. He now can fire as many as ten stars from his ray gun, the stars can be arranged differently, and the pink star turns into a regular purple star when orbiting at ground level, forcing Bowser to keep a better eye on which star was the pink one intially before the stars descend. Fawful shoots out far more energy orbs now, and can reverse the portals which he shoots them through, causing the orbs to come out at the opposite portal from what was originally the case. By far his most notable change is also his most dangerous: Fawful will hold his hand up and summon four dark energy orbs, each one orbiting him. Bowser must rapidly punch at least four Goombas at Fawful through the energy orbs (Goombas which hit the energy orbs will not harm Fawful) to stop him from launching the orbs at Bowser, which lower Bowser's Defense, and deal significant damage to him. However, Fawful himself can take considerable damage from Bowser launching the Goombas at him. When Fawful is at critical health, he will spawn one more energy orb in front of him, moving in a vertical direction, making the timing for Bowser to launch the Goombas at Fawful harder without them being stopped by both the energy orbs surrounding Fawful, and the one moving vertically.
However, if Bowser's power is high enough, Dark Fawful can be defeated without his headgear being inhaled. After he is defeated, the Vacuum Helmet will run away.
After he is finally defeated, Dark Fawful will become unstable, collapse into the Dark Fawful Bug, and flee the room. As soon as he enters the next room he is forcibly inhaled by the incomplete Dark Bowser and becomes the Dark Star Core, which must be battled as a final Boss.
 Names in Other Languages