Kagemamoru is the ultimate villain of Season 1, and was sealed into Alpha in the second episode.
Kagemamoru was originally designed and envisioned as a virus-like guardian for TOME by a mysterious 3rd party developer. It was supposed to act as a sort-of automated GM: punishing those who broke the rules, and so on. Unfortunately when the Kagemamoru was released into TOME it began to rampage. Fearing damage to Motherboard, the Netkings attempted to battle it, but failed, and it was only through both hacking and editing the virtual space around it that allowed the virus to be initially stopped. During the fight, Kagemamoru demonstrated an ability to affect users in the real world. Most of the Netkings sustained minor injuries in real life from the fight, but Zetto, who lost his arm during the battle, suffered the most.
Years later, Kagemamoru was unintentionally freed by Alpha when he managed to find his way into its prison by a glitch. It struck a deal with Alpha, offering him power in exchange for "help." Not knowing any better, Alpha agreed and Kagemamoru attached itself to him. This merger allowed Alpha to go into a "berzerker mode," and allowed Kagemamoru to regain its strength. In the episode 22 fight, Kagemamoru gets drained from Alpha into Zetto's arm, but Kirbopher15 drains Kagemamoru from Zetto into a Drain Sword and then breaks it.
Having regain its strength and no longer merged with any players, Kagemamoru proceeds to continue its rampage. Kagemamoru is defeated by a joint attack by Alpha and Kirbopher, which shatters it into dozens, if not hundreds of pieces.
Kagemamoru, as a virus, is extremely resilient and adaptive. Most attacks don't even phase it, and even if one manages to damage it, it simply regenerates almost instantaneously. Until the Anti-Virus was made by Webmaster, Kagemamoru was effectively immortal; the most the protagonists could do to it was slow it down.
On the offensive front, Kagemamoru uses a variety of moves - ranging from turning parts of itself into projectiles, a purple "whip," forming spikes beneath enemies, and creating a bolt of energy composed of virus stuff.
Affecting RealityEditAs a virus, it has the ability to massively change TOME's environment. This can be as minor as making a unique item, like Kalasu Angel's sword, or as major as tearing up virtual continents. But more than that, Kagemamoru has the ability to directly affect players in the real world through their headset. This ability ends up driving the plot of TTA, even after other villains take the stage, since it is powerful enough to kill people.
Kagemamoru's ability to merge with players is another power that ends up having far reaching effects beyond Season 1. The merger allows the user to call upon some of Kagemamoru's abilities, but in exchange the virus gains a degree of control over the user's mind and body. Further, players merged with wither Kagemamoru or one of its fragments gain some of its ability to affect the real world.
TOME: Terrain of Magical ExpertiseEdit
In episode 1 Alpha#TOME: Terrain of Magical Expertise finds a virus in a similar scenario as Kagemamoru, he offered Alpha#TOME: Terrain of Magical Expertise power to impress his friends with in exchange for his freedom. This virus however is known as Kajet, possibly named after Kajetokun who works on the series' music and is best known for his memetic videos such as "9000!! NINE THOUSAAAAANDD!".
Soon enough, he discovers Kajet's secret area and the virus infects his character, granting him the ability to delete virtual space and cause pain to players in real life. With Kajet in hand, he becomes wrapped in something far bigger than him.