One of the 10 Legendary Warriors. He is the corrupted form of Lowemon, created by Cherubimon and was given to Kouichi Kimura.
Duskmon is a Hybrid type Digimon who's the corrupt form of the human spirit of darkness. He resembles a black skeletal knight with his armor looking like bones while his hands look like a creatures skull, his helmet shares simular features. His eyes are red and he has long pale blond hair, his armor also possesses eye balls which are also red and have been shown to move. His skull like hands hide his two jagged red swords that he can extend at will.
At first, he is reclusive always staying at the hide out, he's shown to be very loyal to Cherubimon as he informed him of Mercurymon and the fact that he had Seraphimons fractal code. Unlike his fellow warriors he did not pursue the children or collect fractal code always staying reclusive. Eventually after a conversation with Mercurymon he decides to face the human children when they enter through the dark gate. After the children defeated Arbormon he made his first appearance and instead of helping his comrade he found him useless without his beast spirit deleting him. The children try to fight him but he proves to be a powerful opponent being able to flip Burninggreymon on his back with ease and take on the children's attacks without flinching.
When they escape him the first time he tracks them down and attacks yet again, using a plan it seems to work when they all attack at once but Duskmon proves them wrong by easily escaping the weak attack. Deciding to end the fight he readys to kill Agunimon when Kendogarurumon gets in the way taking the blow reverting the beast of light back to Kouji. When Agunimon crys out Koujis name it seems to pain and confuse Duskmon as he unleashes darkness on the entire battlefield and escapes. He later reappears going inside Mercurymon's beast spirit and facing Kouji being able to easily defeated the latter, he uses his Memory Disturbance to look through Koujis memories only they bring him more questions than answers. Deciding to kill kouji once and for all he is stopped when the warrior of light becomes Beowolfmon starting the battle again, when the two clash swords in an attempt to destroy the other whats inside duskmons armor only causes both warriors more questions than before.
He and Beowolfmon continue their battle outside of Sakkakumon with duskmon still in confusion of his strange emotions. Beowolfmon and him clash once again and eventually he gets a chance to take down beowolfmon but remembering kouji causes him to hesitate making an opening for beowolfmon to corner duskmon. Cherubimon chooses that moment to interfere attacking beowolfmon and trapping him deeper in the area they battled in. Meanwhile its revealed that duskmon isn't just human he's also koujis older twin brother kouichi, cherubimon using his feelimgs of bitterness and jealously for his twin and father allowed duskmon to once again be free of his emotions by becoming the corrupt beast of darkness Velgemon. Beowolfmon also wanting the truth is unable to even speak to the beast as it savagely attacks him proving to be even more powerful than beowolfmon. Eventually their fight leads them outside once again when Velgemon had used his Zone Deleter a very powerful explosive attack. Being able to easily spot kouji who had reverted back he was about to deliver the killing blow with his talons when Ophanimon was able to speak through koujis D-Tector and once again awaken his human memorys. He leaves in confusion not knowing what to do as kouji is surprised to hear the beast was actually in the human world. Eventually duskmon who had slide evolved back to regain his senses remembered that kouji was his brother, when cherubimon appears he tells his master what he discovered. Cherubimon isn't fazed in the least already knowing this but duskmon admits he cannot fight his brother, cherubimon once again plays on his human heart this time using his memorys of his mother succeeding in his task as duskmon once again searches for kouji. He eventually finds the human as the other questions him only to have to become beowolfmon, once again the brothers clash as duskmon finally reveals to kouji that he is his twin brother.
At first the other denies it as being a lie but after duskmon recalls information he shouldn't know he finally convinces kouji of the truth. At that moment cherubimons darkness takes ahold of him as he becomes velgemon once again and he almost succeeded in killing his brother this time only for takuya to knock kouji out of the attack last minute.
Velgemon trys to attack the two as patamon trys to take him on using his Boom Bubble attack, eventually the young rookie runs out of energy being swatted away like a bug easily. When Aldamon attempts to attack him he easily grabs the fire Digimon and eventually knocking him into Beowulfmon who finally decided to fight. Velgemon is finally defeated by the teamwork of Aldamon and Beowolfmon being reverted back to his human form, though the guilt was what would replace all of his former emotions for awhile.