After the events of "Super Mario 3D World" (2013), Bowser makes his final return to conquer the Mushroom Kingdom with his new found, supernatural power.
After Mario tries to end Bowser's evil rain of terror by using a powerful laser blast, he soon realizes that he killed one of his best friends, instead of Bowser.
Mario and gang learn about eight mystical gems that can bring the princess back to life, then, they go to Bowser's Castle to try and kill the Koopa King.
Waluigi and Shy Guy go out on a search to steal the Primal Gem Mario had recently retrieved. His plan gets spoiled and looks back on his sad life and is then taken over by the dark power that once took Mario.
Mario finishes up his battle with Waluigi. Once he returns, the remains of his crew go out to find the next Primal Gem in a suddenly snowed over land. But on their way they meet and old foe and and old friend, gone evil.
Wario threatens to kill Doctor Toad and Blue Toad, but Luigi heals from his injuries just in time to save them. He then reminds them about the events that took place before Bowser's attack, The Great Mushroom War.
Mario and company find out Donkey Kong was being mind controlled by Lemmy Koopa, and that he has the second Primal Gem. They are then forced to fight against shadow clones of Bowser, Mario, and Peach. And Yellow Yoshi finds his secret hidden power.
Mario and company finish off their battle with Lemmy, but then are soon faced by Bowser Jr. and Kamek. Kamek uses a strange curse on Yellow Yoshi to seal his fate. Mario then goes out to search for Luigi.
Mario goes out to search for Luigi, but instead he finds him along side Bowser and Luigi threatens to kill Mario under the new alias "Mr. L". The rest of Mario's friends come to aid him in an all out battle.
