Morrismon is an unindentified type of Digimon whose name is derived from "Morris worm", one of the first computer worms distributed via Internet. Morrismon was born from a Digi-Egg that was infected by a virus capable of turning other Digimon aggressive. Killing every infected Digimon who has already helped the virus reproduce and downloading their data makes Morrismon even more powerful.
Morrismon's appearance changes when it grows stronger. Its weakest form, Pure Form (strength same as Fresh or In-Training Levels), looks like a small grey-colored Mongolian death worm. Whenever, it becomes stronger its body grows. Its second form, Legged Form (strength same as Rookie), includes Dokugumon-like legs. The third form, Mature Form (strength same as Champion), includes a torso, with two arms: the left hand with big blue claws and the right hand is replaced by a large blue stinger. Its strongest known form, Winged Mature Form (strength same as Ultimate), includes dark green wings, and its legs, claws and stinger have grown longer.
Morrismon was born when one of the Digi-Eggs was infected by a virus created Ronald Yeoman, a man who was the president of the North American division of Digicon Intrnational Enterprises, and powered by Dark Craters, which contained remaining darkness in the Digiversum. The virus was meant to make its victims more violent and kill every other Digimon within its sights. But while infecting a damaged Digi-Egg, the virus restored it and caused birth of an entirely new species: Morrismon.
Morrismon was able to disrupt the dimensional portals between the human world and the Digiversum, but it was also capable of becoming stronger by killing Digimon infected by virus and download their data to itself. Morrismon was too powerful to be killed even by six uninfected Partner Digimon in their Champion forms. But then Keisuke Ishimura and Sven Vestergaard created an antivirus program and downloaded it to their Digivices to have their light to eliminate darkness inside the virus. The Digivices made each Partner Digimon became capable of wounding Morrismon and finally kill it.