Dark Bowser

"Soon, this kingdom will vanish along with all who dwell within. And you, too, will sleep eternally in the dark power's embrace!"

- Dark Bowser

Dark Bowser is Bowser's final boss in Mario & Luigi: Bowser's Inside Story.

Mario & Luigi: Bowser's Inside Story
While the evil Dark Star was gathering DNA from Bowser's body, Mario and Luigi tried to stop it before it succeeded with its goal. The brothers succeeded to defeat it, but it seemed that it already got every piece of DNA that it needed. The only part which was missing were the legs which he gathers by inhaling Dark Fawful, and thus creating a dark version of Bowser. He flees from Bowser. When Bowser finds him in the secret tower,they both breathe fire at the same time, starting an epic duel. Bowser overwhelms him, then they both curl up into a spike ball and the fight commences. Bowser again overwhelms his Dark form, who then covers the whole Mushroom Kingdom in darkness, with Bowser being the only one who could defeat him. Eventually, sick of the battle of the titans, Bowser charges up his fists and gives the dark version the final blow.

One of Dark Bowser's attacks is throwing a boulder into the air and blasting it apart, causing rocks to fall out of the sky. Bowser must use his shell to avoid taking damage. However, he must also punch one of the rocks at Dark Bowser, who is charging an attack. When the rock lands in his mouth, it plugs him up & causes his attack to damage him from the inside. If he does not, then he is blasted by dark fire.

Another attack has him punch Bowser repeatedly. Bowser must counter with his own punch. The two giant blows meet, and throw the titans back, creating a shock wave. Then Dark Bowser will jump into the air as a spiked ball and tries to land on Bowser. Bowser must retract into his shell to avoid taking damage. He can then counter attack by quickly throwing a punch at Dark Bowser. Another attack is trapping Bowser in a cage and raising it into the sky. He will then charge up an energy ball. Bowser must try and destroy the cage's lock before he gets hit by the energy ball. He can also swing the cage off its hinges with shell defense to damage Dark Bowser. After taking enough damage Dark Bowser will fall to the ground, but then gets healed by the ingested Dark Fawful and will grow giant. He will always follow this up by tossing a mixed ball of "Dark Minions" at Bowser, including Goombas, Koopas, Thwomps, Bob-ombs and Bullet Bills. Bowser must then walk back through the "Dark Minions" Back to Dark Bowser. When he catches up, Dark Bowser again curls up into a spike ball and tries to body slam him. Bowser must curl up into his shell, then do it again as Dark Bowser prepares the next body slam. Bowser has to punch him in the stomach so that he spits up Fawful and then inhale him, which Dark Bowser will try to do as well. Inside, the Mario brothers must fight Dark Fawful, only after which can Bowser give his doppelganger the final blow.

When Dark Bowser is incomplete, he speaks extremely slowly. However, as he transforms into his final form, he starts to speak fully.
 * HP: 1000

Quotes
Main article: List_of_Quotes_in_Mario_&_Luigi:_Bowser's_Inside_Story