"The Cannibal left his sack of paralytic fear and tore us all apart!"
The Cannibal's Reign was a time where Kirby, a cannibalistic serial killer from Dream Land, plagued various different nations, including Dream Land, Hyrule, and the Mushroom Kingdom. During his time in the Mushroom Kingdom, he was pursued by another vigilante from Dream Land named Meta Knight, who was obssessed with hunting him. Kirby's reign was devastating, as it sent the nations that Kirby haunted into poverty, which would eventually result in the War of the Elite. Kirby, after killing a civilian named Daisy, was captured by the Super Mario Brothers and institutionalized at Petal Meadows Asylum. However, his legacy would live on, and he would eventually break free from prison during the Butchers' Reign and presumably began to haunt the Mushroom Kingdom again.
"Believe me, I too have had my share of monsters."
Kirby was originally from Dream Land, where his terrible reign began. It is unknown what the cause of his insanity is, as is how he began his reign. However, his launch on Dream Land was devastating enough to send it into enough chaos to make it nearly uninhabitable for civilians, enough that its ruler, King Dedede, left and took refuge in the Mushroom Kingdom. Meta Knight, a major hero of Dream Land, left his own land to die as he pursued Kirby, having grown an obsession with the serial killer.
At some point, Hyrule was attacked by Kirby. It is unknown what effect he had on the nation, but it was likely devastating.
"The Cannibal took a liking to the city, enjoying the xenophobic misery of it. The perfect killing ground."
Kirby's attack on the Mushroom Kingdom was his most infamous action. It is unknown when this occured, though it is implied that it happened after the Fall of Hyrule During this time, he arrived at the Mushroom Kingdom. Enjoying the "xenophobic misery" of the civilians, Kirby decided to stay there and haunt it. Kirby killed several people, turning the once peaceful and happy nation into a terrified and chaotic nation.
Here, several authorities gathered to capture Kirby, including those from Hyrule, such as the Super Mario Brothers, Princess Peach, Police Chief Link and Princess Zelda of Hyrule. However, Kirby made sure not to leave any patterns, making it difficult to find him.
Later, Meta Knight came to the Mushroom Kingdom to hunt down Kirby. The authorities of the Mushroom Kingdom found him and convinced him to cooperate with them. Meta Knight, having studied Kirby and learned much about him, proved to be an extremely valuable asset in finding him. Eventually, they found Kirby dancing around in Daisy's skin after he had killed the latter. Princess Peach ordered him condemned to Petal Meadows Asylum, where he would remain for six years.
"Do you hear them princess? Do they still whisper my name? Has this... butcher, opened up the wound your subjects have long since scabbed?
Despite his reign having ended, Kirby's legacy lived on in the poverty of the nations that he had haunted. People even feared to speak his name, instead referring to him as the Cannibal. However, some people were willing to speak his name, including Mario, Link, Wario, Luigi, Princess Peach, and Meta Knight. However, Mario and Luigi advised Princess Peach from interrogating Kirby, remembering his dark past. Kirby had even left behind something else besides the fear...
During his reign in the Mushroom Kingdom, Kirby sought out Mewtwo, a corrupt, psychic Pokemon. However, he did not feed that day, but instead he "whispered." What he did to Mewtwo drove him insane. Mewtwo became a mafia don, and in his madness, decided to raise an army of psychic children. However, due to deadly rumors about his activities, his army would never come to be. Mewtwo made the mistake of keeping two of the children for himself. These two children would later come into the possession of another mafia don named Ganondorf Dragmire, the Shadow Don, who turned them on their master and used them to kill the other two dons, starting another terrifying killing spree.
During this time, Kirby would break out of prison during a raid lead by Mario. Kirby would find Ness and Lucas in the Ivory Towers during a battle occuring near it, but before he could bring them with him, an explosion caused by Luigi stopped him in his tracks. While it is unknown what became of Ness and Lucas, Kirby survived, presumably starting another reign of his.