The Corpse Party

The Corpse Party was an event that occurred in Super Mario Continuance (REITERATED). It was a horrible calamity where bodies fell from the sky. Though seemingly inexplicable, something Len says at the beginning of the book may stand out to an attentive reader. "If I die, the world will be flooded by the bodies that I store in World 0. And all that has ever been on this planet will cease."

Finale
Once the Corpse Party started, kingdoms around the world were thrust into chaos. Riba and his team were stuck in the middle of it on their way to Abor's Cave. This serves as a great detriment to their journey. Riba escaped the storm of bodies and reached Abor's Cave, while his friends were swept away. Riba planned to take his own life, knowing that with Len gone, he would not reiterate into a new body. He was tired of losing everything that's precious to him. He had lost all hope. However, Mario's spirit approaches him at the last moment and convinces him not to take his own life.

The Corpse Party becomes a lesser threat to Riba as he continues further down into the seemingly endless caverns for hours, though as the narrator states, Riba could hear upper levels of the cave breaking down due to the pressure of the bodies. This implies that the Corpse Party will not stop for a while, and will only grow.

During Riba's fight with Allen, the antagonist, the bodies pelted them in the face, but served as only a mere annoyance due to Riba and Allen's newfound giant forms. As other members joined in on the fight, the pile of bodies grew.

Riba ends up losing the fight. Allen kills him and everyone else. The world is swarmed by bodies, and all comes to a close.

Aftermath
Sometime after the bodies stopped falling, the bodies disintegrated into the Earth. Len, having apparently negotiated her way out of Hell, reiterated everybody one last time. Mario, Riba, Luigi, all of them, get to live a happier life.

Trivia

 * The Corpse Party is named after the video game series of essentially the same name.
 * This is because the game Super Mario Continuance (REITERATED) is heavily based on, (MARIO) The Music Box, is loosely based on Corpse Party, even borrowing some of its music.