Clash of Dimensions is the Story Mode in Super Smash Bros. Riot, similarly to the Adventure Mode from Brawl, The Subspace Emissary. The story takes place in various locations from Nintendo series, it has a similar length to that of the Subspace Emissary and co-op multiplayer is optional.
Like in Brawl, the story is set in The World of Trophies. One day, a dark cloud of ice arrives the world's lands and starts causing havoc by spawning armies of ice soldiers. The ice soldiers and the cloud are commanded by a mystical demon, Lissandra, who wants to turn the different dimensions into ice and make it her own dimension as an ice empire. It's up to the heroes of Nintendo to unite forces and defeat this evil entity.
The story begins with Mario practicing at the garden of Peach's Castle with various Sandbags while both Peach and Yoshi watch him. After Mario finishes, Peach is seen looking at a “Smash Festival” invitation. She calls for Mario and Yoshi and the three leave for the festival afterwards. In their way, a giant, dark blue cloud appears out of nowhere, and ice shards start raining. Along with the ice shards, a mysterious army of ice soldiers fall from the clouds as well, and start attacking. (Stage 1: Defeat 30 enemies) (Playable characters: Mario, Peach, Yoshi) The three keep fighting more Frozling Soldiers, but after a few seconds, both Mario and Yoshi hear a scream from Peach, who has been kidnapped by a much bigger Frozling that escapes into the clouds along with her and the rest of the soldiers. After that, the clouds start moving again and Mario and Yoshi decide to go to the Smash Festival to ask for help. (Stage 2: Mushroom Plains) (Playable Characters: Mario, Yoshi) Upon arriving the Smash Festival, Mario and Yoshi notice that the clouds arrived there earlier and only a few fighters were found trying to defeat Frozling Soldiers, those fighters being Link, Kirby and Pikachu. Before Mario and Yoshi decide to help, a powerful dust appears behind them, trapping both of them inside and then turning into one of Kirby's oldest rivals, Kracko. (Boss Battle: Kracko) (Playable Characters: Link, Kirby, Pikachu) Upon defeat, Kracko vanishes and releases Mario and Yoshi, and the rest of the Frozlings retreat. The five then chase after the cloud to save Peach. The scene switches to Pit, who is watching the events via fountain. Willing to help, he asks for Palutena's permission to help the crew, and with a worried look on her face, she allows him. Pit flies off to chase the dark clouds as Palutena sighs and starts watching him by using the fountain. (Stage 3: Angel Land) (Playable Characters: Pit)
The story changes to a small igloo on an ice summit where the Ice Climbers, Popo and Nana, are taking a nap. Their sleep is interrupted by a loud storm, and both decide to go outside and see what's going on. Several Frozlings are surrounding the igloo, and one of them casts a magic spell on the terrified Ice Climbers, freezing them. A few Frozlings take the frozen Ice Climbers and are about to retreat, but a powerful electric blast lands on them, defeating some Frozlings and releasing the Ice Climbers from their icy prison. The one that shot the blast reveals himself afterwards, being Fox. The Ice Climbers jump happily and start hugging the annoyed fox in gratitude, who pushes them away and points forwards, where more Frozlings start spawning and prepare to attack. (Stage 4: Defeat 40 enemies) (Playable Characters: Fox, Ice Climbers) After defeating the Frozlings, Fox walks away and goes towards his Airwing, which was near the igloo. Before he gets into the Airwing, the Ice Climbers jump into it first, indicating that they want to help him. Fox makes another annoyed face and allows them to go with him. They finally enter the Airwing and fly off.
The scene then changes to a forest, where Captain Olimar is seen walking with a worried expression. Lost in the forest, Olimar decises to sit down along with his Pikmin to think about what he should do. Suddenly, he starts hearing a beautiful tune, and follows the origin of its sound. He then finds Zelda, playing an harp. He gets close to Zelda, sits down and listens to her beautiful music. However, surrounding trees start shaking, interrupting Zelda, and several Tikis approach them, and their leader Tiki Tong attacks. However, before they reach Zelda and Olimar, Donkey Kong appears along with his friend Diddy Kong and hits him, interrupting his attack. Angry, Tiki Tong calls more Tikis, and starts a battle against them. (Boss Battle: Tiki Tong & Tikis) (Playable Characters: Donkey Kong, Diddy Kong, Zelda/Sheik, Captain Olimar) After defeating him, the Tiki Tak Tribe retreat and the Kongs salute Zelda and a nervous Olimar. The cloud appears once again, attacking with various ice rocks. The four decide to exit the forest in hopes of escaping the clouds. (Stage 5: Jungle Hijinx) (Playable Characters: Donkey Kong, Diddy Kong, Zelda/Sheik, Captain Olimar) The four successfully exit the forest only to find Bowser, who rams towards them using his Koopa Clown Car, damaging them and kidnapping Zelda. The three then get up and watch Bowser flying towards the clouds along with Zelda, laughing evily. Donkey Kong and Diddy Kong chase after the clouds to save her, and Olimar, still afraid, follows them.