Myotismon is an Undead Digimon whose Japanese name and design are derived from the mythological Vampire and Demon, and whose English name is derived from the Greater mouse-eared bat. As the king of Undead Digimon, it was resurrected through the dark arts and obtained mighty powers. Originally a brutal computer virus which destroyed the computer data it absorbed, it possessed the ability to revive the destroyed data as malignant computer viruses. As the owner of an extremely cruel and cunning personality, it is exceedingly difficult to destroy this Digimon. However, it cannot demonstrate its powers outside of the night, and its power is cut in half during the daytime.
Myotismon lives in Greylord Mansion, where he is originally found starving on the floor. Once the player brings him Steak, Myotismon explains the situation but later becomes imprisoned by his own creation, SkullGreymon. Once freed, Myotismon reappears in his mansion and a notorious glitch occurs where a large portion of his speech is missing. Myotismon can be obtained with a cheat device.
Myotismon will appear in Thriller Ruins after the Quest given by Digitamamon in Dawn, or Devimon in Dusk.. Myotismon digivolves from Devimon, it requires 195 Spirit, 10,000 Dark Experience, and level 42. It can digivolve to VenomMyotismon, at level 66, 6666 beast experience and a DemiDevimon in the "party". It can DNA digivolve with Shadramon to form MaloMyotismon at level 68, 470 spirit and have Arukenimon in the "party".