Calumon

 Calumon's immature antics and over-expressed emotions leave little doubt about the fact that its role is not of a fighter. Calumon is the only Digimon on the protagonist's side who had no official tamer, although he does seem to have a special bond with Jeri as he was able to sense her presence when she was trapped inside of the Kernel Sphere. He then led Beelzemon in a rescue mission to save her, and helped her immensely when he finally snapped her out of her depression and protected her from the Chaos with a forcefield during the final battle. He may have become her new partner after the events of the D-Reaper Saga of Digimon Tamers. In the beginning of the series, Calumon thinks of the Real World as a game and the humans as other digimon. His ears, usually short, can be expanded, usually when Calumon is happy or excited, to the size shown in the picture to allow him to "fly". His forehead bears the symbol which is the polar opposite of the Digi-Hazard. It is called the "Zero Unit." It is from the Zero Unit symbol that Calumon releases his power to catalyze Digivolution.

In The Series
Calumon is a unique digimon who does not Digivolve, and cannot be Digi-Modified. However, he seemed to use a "Crystal Matrix" when Growlmon first became WarGrowlmon, suggesting that Calumon powers Digivolutions. Another instance of this ability is when he was very excited in the Digital World. This created a trail of shining light that digivolved some Woodmon into Cherrymon. Calumon is shown he is the light of digivolution, knowing that he sent out a wave of digivolution and so every digimon digivolved to mega level.

The Digimon Sovereigns reveal that Calumon originated as the element of Digivolution. In order to hide this power from the evil D-Reaper, they turned the power into the form of a Digimon. In the end of the series, the Sovereigns restore this power to the Digital World, but allow Calumon to continue to live as an ordinary Digimon.

Calumon plays a pivotol role in the last few episodes of the series detecting Jeri's presence and launching a rescue mission for her with Impmon for back-up. Thanks to Beelzemon Blast Mode (Impmon digivolved to fight off some D-Reaper Agents) he gets into the Kernel Sphere where Jeri is and does his best to snap her out of her depression. He ultimatly succedes getting her to fight back against the D-Reaper and to realize that there is something worth living for. After she cracks the Kernel Sphere with her D-Ark, freeing them but letting the Chaos Mass in, he somehow protects them with a forcefield and gets them outside the Sphere. The two are eventually resuced by Takato with help from Guilmon. He is forced to return to the Digital World with the other Digimon at the end and says his goodbyes to a grateful Jeri. At least, until the events of "A Sticky Situation."

Calumon, upon arriving back in the human world, continued to be a constant part of the Katou household even after Jeri gained her own partner back. He remained in the background until Impmon attempted to leave for the digital world in "The Secret of the 327th." The cute individual managed to accompany Impmon and Behemoth there.