|Dub Name||Black Gear, Dark Gear|
A Black Gear (黒い歯車 Kuroi Haguruma) is a device made by Devimon to control other Digimon on File Island, often sending them on an uncontrollable rampage and corrupting their thoughts. The Black Gears also possess the power to strengthen and enlarge Evil Digimon like Devimon. Evil Rings and the Evil Spirals later created by the Digimon Kaiser share a similarity to them. Black Gear will either insert themselves fully into their digimon or will only go parsally with half of it sticking out. When a Digimon is defeated in battle the Black Gear will launch itself out of their bodies and explodes.
The Chosen Children see a Black Gear fly at the beginning of Episode 4, "Red Hot! Birdramon". Upon reaching the Pyocomon village, one of them mentions it saw the Black Gear going to Outlook Mountain. After talking to all the Pyocomon, Yagami Taichi and Takenouchi Sora confirm the direction it flew in. After the Chosen Children defeat Meramon, the Black Gear leaves his body, and they realize it was the cause of his berserk state.
In Episode 5, "Lightning! Kabuterimon" the Chosen Children discovers Factorial Town. The Chosen Children finds Andromon stuck in between Factorial Town's gears. While they are trying to free him a Black Gear enters Andromon's body causing his to identify the Chosen Children as enemies. After Andromon is defeated the Black Gear leaves his body.
In Episode 6, "Palmon Angrily Evolves!" all of the Chosen Children besides Mimi are captured by Monzaemon, and are forced to be played with by all the abandoned toys in Toy Town. After being defeated he just wanted kid to value thier toys more, but an evil feeling created from the Black Gear overwhelmed him.
In Episode 7, "Roar! Ikkakumon" Jou climes Infinity Mountain to see if it safe for the rest of the Chosen Children. Jou witness a swarm of Black Gears emerge from the top of Infinity Mountain. Jou then sees a Black Gear laugh itself into Unimon neck.
In Episode 8, "Messenger of Darkness, Devimon!" Devimon commands Ogremon and Leomon to destroy The Chosen Children. When Leomon refuses Devimon insert a Black Gear into him, It is momentarally removes when Leomon came into contact with Tai Digivice but was promply returned inside Leomon.
In Episode 9, "Clash! The Freezing Digimon" Tai is stranded on an iceberg and is attacked by Frigimon with a Black Gear sticking out of it's back. Tai then meets up with Matt when they are ambushed by Mojyamon with a Black Gear laughed in his chest.
In Episode 10, "Centalmon, The Guardian!" Mimi meets up with Izzy, they have a fight and Mimi is lost in a maze, while trying to find a way out they faced off with Centarumon. After being freed from the Black Gear Centarumon helps the Chosen Children chase off Leomon.
In Episode 14, "Departure - to a New Continent!" the Chosen Children builds a raft to travel to Server Continent. while on their way they are eaten by Whamon, and finds a Black Gear in Whamon's stomach. As thanks Whamon took the Chosen Children to an underwater store, but were ambushed by a Black Geared Drimogemon.
The Digimon taken over by the Black Gears includes: