|“||True power awakens when the light and darkness inside coexist and merge into one single source of power.||„|
Mastemon (マスティモン ?, Mastemon) is an Ultimate-level Holy-species Angel Digimon who is a member of the Boundary Crossers, a group of Digimon that travel between universes to retrieve any rogue Digimon that may have escaped the Digital World.
Mastemon was one of the first members recruited into the Boundary Crossers by Darkdramon. Her power to cross the borders of spacetime immediately drew the Dragon Digimon's attention, as he needed at least some means to travel through spacetime to set out on his mission. Mastemon was not the easiest to convince at first, but it was eventually the newly-recruited Dukemon who managed to convince her to join the Boundary Crossers. Surprised, Darkdramon commended Dukemon on his first accomplishment in the team. With one of their key members in tow, the Boundary Crossers kept searching.
Mastemon is very sweet and kindhearted, even when on the job. She tends to merge her professionalism with her kind disposition and, as such, is often assigned to ask around about the rogue Digimon. She is also the one to keep the group together if they are internally divided on matters, stepping in to tell them not to fight among each other. While normally quite calm and contained, Mastemon is not shy about her huge crush on Dukemon, which happens to be mutual, fortunately for her. She unabashedly shows her love for Dukemon by being around him whenever they are together and giving the knight a big hug when seeing him again. The other Boundary Crossers sometimes joke around with them as a couple, but neither of them really minds. Mastemon has her moments of vanity, which clashes with fellow team lady Diablomon, who couldn't care any less about her own looks; as a result, the two often end up bickering, though that is usually just butting heads (sometimes literally) and snarling little insults.
- Dark Pentagram: Mastemon creates a pentagram underneath her opponents that traps them in a black void, reducing their elemental resistances.
- Final Heal: Mastemon casts a healing light over herself and her teammates, restoring their HP.
- Demon Blast: Mastemon fires a powerful wave of concentrated dark energy at the opposition from her left hand.
- Royal Cannon: Mastemon blasts a massive beam of light energy at the opposition from her right hand.
- Chaos Degrade: Mastemon concentrates the essences of light and darkness and combines them to form a gate that briefly traps the enemy in a different dimension.
Mastemon is capable of travelling through spacetime; this ability is pivotal in the Boundary Crossers' mission, hence why Darkdramon took interest in her and wanted her to join the team. Mastemon combines her powers with GigaSeadramon's internal spacetime oscillation waves to create a stable Digital Gate for only the Boundary Crossers and affiliates to utilize; only those with a BC Pager can traverse these special Digital Gates.