This article is about the final boss of Bowser's Inside Story. For the form of Shadoo, see Dark Bowser (Shadoo).
Dark Bowser is the transformed state of the Dark Star after absorbing Bowser's DNA, and a final boss in Mario & Luigi: Bowser's Inside Story. He is much more evil than Bowser, wanting to destroy everything rather than rule it.
When the Dark Star absorbed Bowser's DNA, it became Dark Bowser, but was incomplete due to Dark Fawful having absorbed its energy. So Dark Bowser searched for Dark Fawful. He inhaled Princess Peach before he finally found Dark Fawful and inhaled him, becoming a complete Dark Bowser. Bowser chased him down, at one point engaging him in a spike ball battle, until they reached the top of Peach's Castle. Dark Bowser began to shroud the world in darkness, but Bowser wanted to rule the world himself and wasn't about to let a more evil villain destroy it.
Bowser fought Dark Bowser and eventually defeated him, but Dark Fawful, combined with the Dark Star Core, fully healed him. Bowser made him spit out Dark Fawful and then inhaled him. Mario and Luigi fought Dark Fawful and the Dark Star Core, and this repeated until the Dark Star Core was destroyed, immobilizing Dark Bowser and rendering him unstable. Without Dark Fawful to heal him, Bowser was easily able to finish him off, and he was completely destroyed, restoring light to the Mushroom Kingdom.
Dark Bowser has 1000 HP. He attacks by punching Bowser, which Bowser must counter with his own punch. Dark Bowser will then try to body slam Bowser, but Bowser must duck to block this, and then punch Dark Bowser as he stands in front of him. He can also throw a boulder into the air and destroy it to make falling debris fall on Bowser. Bowser can punch the ones that land in front of him, and duck to block the ones directly above him. If he does not punch a rock at Dark Bowser, then Dark Bowser will breathe fire at Bowser for some massive and unavoidable damage. Dark Bowser also traps Bowser in a cage of dark energy and powers up to shoot a dark energy ball at Bowser, but by repeatedly tapping X to punch the cage, Bowser can destroy it in time to fall and avoid the attack. When Dark Bowser's HP reaches zero, he will fall, but Dark Fawful will heal him for all his HP. He will then increase his size and throw a ball of Koopa Troop enemies at Bowser. Bowser will automatically fight them off. Bullet Bills must be punched or ducked, Bob-ombs can be punched to blow up other enemies, Thwomps can be blocked by ducking them, and Koopas can be punched, also striking ground enemies. Goombas are the least of Bowser's concerns and can be punched to defeat them.
Bowser must then attack Dark Bowser's stomach. Regardless of damage (which is greatly reduced in this form) this will make him spit out Dark Fawful the bug, and Bowser must then inhale him. Dark Bowser will try to inhale him as well, so Bowser must overpower him in this. If Dark Bowser inhales Fawful, Bowser must repeat the whole process all over again. If Bowser inhales Fawful, the Mario Bros. do their part of the final battle and fight him and the Dark Star Core, which is the main target of the battle. Only when it is destroyed can Bowser deliver the final blow. The player must press X repeatedly, several times. There is no time limit and the unstable Dark Bowser cannot fight back. The last time requires more pressing X, so that Bowser will destroy Dark Bowser with a Sliding Punch.
- This is the second final antagonist who is directly destroyed by Bowser and indirectly by the Mario Bros., the first being Elder Princess Shroob, whom the Mario Bros. tricked Bowser into hitting with his fireballs.