Dark Star

Mario & Luigi fight Dark Star X

The Dark Star is an artifact featuring prominently in Mario & Luigi RPG 3. Long before the time of the game, it was hidden away beneath Toad Town due to its Powers of Darkness.

During the events of the game, it was stolen by Fawful in order to fulfill his plans. He uses its power to barricade the front door to Peach's Castle allowing him to use it as a stronghold during the game. The Marios eventually use the Miracle Vaccine to destroy the barrier.

When Bowser confronts Fawful and Metaboss near the end of the game, the Dark Star escapes from the machine that Fawful has been using to drain its power. While Bowser is distracted fighting Buribādo Metaboss, Fawful absorbs some of the Dark Star's power, and is converted to Dark Fawful. He flies off in search of the missing star.

However, while he is gone, the Dark Star returns and invades Bowser's Body. Thus, the Marios venture to the final unexplored area of Bowser's body, Air Space. Here, they discover the Dark Star absorbing pieces of Bowser's DNA. They attempt to capture it several times, but each time it escapes using one of Bowser's powers. Yellow Star theorizes that it is somehow incorporating Bowser's DNA into its own body.

Eventually, the Marios confront Dark Star at the very back of Air Space. They attempt to destroy it, but it simply escapes from Bowser's body. Outside, it transforms into an apparition of Dark Bowser and escapes, freeing Bowser from the room he was trapped in in the process.

Later, when Bowser defeats Dark Fawful, he becomes a small blob of dark power and escapes. The still incomplete Dark Bowser absorbs Fawful and uses the power he took to complete his body.

The Dark Star's final appearance is during the final battle. After Bowser does critical damage to Dark Bowser, what remains of Fawful heals him fully and causes him to double in size. At this point, Bowser attacks Dark Bowser's belly, causing him to expel Dark Fawful. Bowser absorbs Dark Fawful for the Mario Bros. to handle. Here, he transforms into a giant insectoid mass of dark power, still with his manic grin and now crimson eyes. His only weakness is the Dark Star Core, which sits on an antenna high above his head. As with the final bosses in the previous two games, the Marios must progressively disable the different parts of Dark Fawful before attacking this weakness. It is likely that it still has a distinct intelligence from Fawful's, since he is visibly displeased whenever it decides to flee.

Dark Star reappears in the Battle Colosseum as Dark Star X. It costs 2500 coins to battle and must be defeated in twelve turns.