Myotismon feeds on the fresh or deleted data of his victims, though he developed a taste for human blood during his stay in Odaiba. His victims were thought to have been afflicted with sudden anemia. His power depends on the absence of the sun, although he seems to be able to overcome this by creating a fog around wherever he goes. He has demonstrated telekinetic abilities at times - such as halting and crushing a rock thrown at his head with his thoughts, and moving MegaKabuterimon's body into WereGarurumon when he was about to attack him, although the latter could possibly be attributed to the fog which Myotismon amplified using the TV station in Tokyo, as he resorted to his Grisly Wing to counter Garudamon's Wing Blade in the digital world, and to melee combat in his duels with WereGarurumon and MetalGreymon. They both failed then Gatomon digivolved into Angewomon and destroyed Myotismon but then he digivolved into VenomMyotismon.
After the eighth child, Kari, reveals herself in a vain attempt to stop the fighting, Myotismon places all the hostages in a deep sleep before easily overpowering the combined forces of the Digidestined as they attempt to save Kari from him. When Myotismon kills Wizardmon with a attack meant for her, Kari's Crest glows, causing Gatomon to digivolve Angewomon, and allowing her to defeat Myotismon by combining the other Digimons' power with her Heaven's Charge and forming it into her Celestial Arrow. However, Myotismon is not truly dead, but only weakened, with his core remaining in his mask. As his Alpha Bats steal energy, Myotismon takes on a shadowy form and begins to recuperate. After the dazed hostages in the Convention Center start chanting his name, the Digidestined realize that the prophecy Gennai contacted them about was coming true, and by the "Hour of the Beast" (6:06:06 PM) Myotismon absorbs all of his Alpha Bats and obtains sufficient energy to digivolve to VenomMyotismon. However, in this form he has lost most of his intelligence, and has an uncontrollable desire to eat and destroy, even going so far as to devour DemiDevimon before heading towards the Convention Center to eat the people there. However, by fulfilling the end of the prophecy that foretold Myotismon's resurrection, the Digidestined manage to get Agumon and Gabumon to digivolve to WarGreymon and MetalGarurumon, who succeed in defeating him with the help of the other Digimon and the power of the crests. Although VenomMyotismon is again thought to be destroyed, his "spirit" endured and possessed Yukio Oikawa, setting in motion the events of Digimon Adventure 02.
On December 31, 2002, at the climax of his scheme, Myotismon opens a Digital Gate, removes himself from his host, and uses the power of the Dark Spores to assume the form of MaloMyotismon.
Upon his resurrection, he tortures and kills Arukenimon with the excuse of testing his new found powers. After Mummymon attacks and is killed by MaloMyotismon in an attempt to avenge Arukenimon, Davis is the only one still willing to overcome his fear and fight someone as sadistic and merciless as MaloMyotismon. Fueled by his courage, ExVeemon attacks MaloMyotismon with everything he has, and succeeds in doing some damage. MaloMyotismon tries to incapacitate the team by using their desires against them, but since Davis' greatest desire is to see MaloMyotismon defeated, he is able to break free of the spell and rescue the others. Davis' desire also enables all the different forms each of the Digidestined Digimon to appear simultaneously and form an army which unleashes a massive series of attacks that seriously injure MaloMyotismon. However, it is revealed that this actually broke open a portal to the Digital World, allowing MaloMyotismon to escape to it and recuperate where he is most powerful.
He posed a challenging battle for the DigiDestined, who were not able to defeat him even with all the Digivolved forms of their Digimon. During the fight, very many Digimon, as well as the main DigiDestined's partners appeared on the edge of the canyon, and MaloMyotismon launched his Screaming Darkness attack on them where all the DigiDestined encountered appeared in the Digital World. Again, the help of the Digivices was required to defeat him — it took the light from every Digidestined's Digivices to cause Myotismon's body to dissolve into a dark spirit, and then to modify Imperialdramon Fighter Mode's Positron Laser, which he used to fire his Giga Crusher, completely destroying Myotismon.
Myotismon was revived by Millenniummon and instructed to keep two of the Digidestined prisoner in the Wonderswan games Anode/Cathode Tamer. Upon facing the protagonist, Ryo Akiyama, Myotismon praised Millenniumon's power and declared he would cut off Ryo's head and send it to his master as tribute.
VenomMyotismon is Myotismon's Mega form, a Dark Beast Digimon. Though he is much more powerful, he is also much less intelligent and has an insatiable hunger, at one point devouring his own servant, DemiDevimon. In the prophecy revealed by Gennai he is called the "Undead King" (or "King of the Undead" by DemiDevimon) and when the clock strikes the hour of the beast, he would reveal himself in his true form as the Beast. His "true" body is actually hidden in his abdomen, and rarely comes out (it isn't until War Greymon drills a hole through his abdomen that his true form, the "Beast Within" appears). He is the first Mega Digimon to be introduced in the series and it is because of his appearance that the Digi Destined learn about the Mega level.