It serves as the main antagonist in Kirby's Dream Land 3 and Kirby 64: The Crystal Shards (as his resurrected form 0²). It is a mysterious being who resides within the Hyper Zone who desires to spread Dark Matter across the universe and turn it into a "Dark World". Though it was defeated in Kirby's Dream Land 3, its kind would continue to serve as recurring foes for Kirby.
Kirby's Dreamland 3
After the defeat of Dark Matter Blade, 0 launched an invasion of Pop Star and possessed multiple regions. Kirby liberated these lands one by one, then encountered the Dark Matter possessed King Dedede. Kirby drove it out of him and back to the Hyper Zone where 0 resided.
After Kirby and Gooey defeated the Dark Matter using the Love-Love Stick, 0 revealed himself and attacked Kirby. In a desperate attempt to kill Kirby, 0's eye detached from his body, becoming a small bloody eyeball. Kirby defeated this, thus destroying 0 and the Hyper Zone.
Kirby 64: The Crystal Shards
0² serves as the main antagonist and the true final boss in Kirby 64. Like Zero, it remains hidden throughout the majority of the game, until the end when the player has managed to collect all of the crystal shards.
In this game, 0² has an angelic appearance and a bandage on his head (which is likely a reference to him pulling his eye out at the end of Kirby's Dreamland 3). In order to face the creature, Kirby must collect all 74 crystal shards, otherwise Miracle Matter serves as the final boss.
- Several fans have considered 0 one of the scariest bosses of all time in both of his appearances.
- Oddly enough, a cactus-shaped tail seems to protrude from 0², which is his weak point.
- Some fans have speculated that Dark Mind, the main antagonist of Kirby & the Amazing Mirror, is an alternate-dimension version of 0, although he may actually mirror the Nightmare Wizard from Kirby's Adventure.
- Many later villains in the series bear resemblance in a way to 0:
- Dark Mind appears as a giant ball with an eye.
- Drawcia Soul appears as a giant ball with a mouth that strangely resembles an eye.
- Dark Nebula is a source of darkness, with the power of possessing others.
- Magolor, when defeated, is completely overtaken by the Master Crown and has a giant eye with a red pupil in his mouth, which almost completely resembles 0.
- Also the fact that Magolor is in charge of a race of monsters.
- Void Termina's Core, Soul, and Void all appear as giant balls. His face can arrange itself to appear as the smile 0² makes.
- Some fans have theorized the Master Crown in Return to Dreamland had a portion of 0's soul within it.
- Because 0 hemorrhaged and bled on screen (and shot blood at Kirby as he attacks, as well bursting out the rest of his body in a gruesome, gory scene), he has often been depicted as the most gruesome character in Kirby history.
- During the fight with 0², the "Try Again" option is replaced with "Tough It Out!". This option has the same effect as "Continue".
- The bandage on 0²'s head may be a reference to when his eye separated from the rest of his body in Kirby's Dream Land 3. This would mean that there is a gaping hole beneath the bandage left from when the eye broke away.
- Due to this and the bandage from Kirby's Dream Land 3, 0² could be considered 0 the second. This also means that the 0's red eye is his actual appearance and that the white sphere it inhabits is merely an egg sack containing numerous developing baby Dark Matter scouts that 0 uses to attack Kirby when they emerge from it.
- A remix of 0²'s theme is an unlockable song in Super Smash Bros. Brawl by collecting at least 5,000 coins in coin matches. The remix also appears in Super Smash Bros. for Wii U and Super Smash Bros. Ultimate as default songs.
- Many people have considered 0² to be one of the most disturbing bosses Nintendo has ever made (along with Giygas from EarthBound and Mad Jack from Donkey Kong 64).
- Zero and 0² are the only Kirby bosses to actually hemorrhage when hit; Zero used his blood as a weapon, while 0² bleeds from his eye when attacked.
- In Return to Dreamland, Magolor's final form appears to have lost control and is merely a sad shell under the influence of the Master Crown, bearing a resemblance to a Dark Matter creature (even his mouth morphs into a Dark Matter eye) - this could mean that Zero is indeed still alive and manipulating his new host through the Crown, or else, from inside the Crown.
- In the Soul Melter EX difficulty of The Ultimate Choice from Kirby Star Allies, when fighting Void, his color scheme is similar to 0. Also, his splash screen resembles the Hyper Zone where 0 was fought.