Isoc is a mysterious Reploid scientist who works alongside Gate in Mega Man X6. Almost nothing is known about him, though he aids Gate with his plans to build a Reploid-scentric society by coordinating the efforts of the Nightmare Investigators and also by making public speeches regarding the Nightmare crisis.
If Zero defeats High Max in one of the secret areas, Isoc watches it and starts laughing uncontrollably. When Zero asks why he is laughing, Isoc responds that he cannot help it after seeing how powerful Zero is, pointing out that while X could not defeat High Max, Zero has done it so easily. Zero then tries to attack Isoc, but Isoc raises his hand and nonchalantly generates a force field that immobilizes Zero, saying that he knows him inside out and can capture him at any time. Isoc than retreats with High Max. Alia notes that Isoc's field has a deactivation timer, and wonders why Isoc had the trouble to only trap Zero without harming him. In X's version of this scene, Isoc swears to personally destroy that "ancient piece of junk", indicating hatred towards X, but for the time being he withdraws with High Max. X tries to go after them, but listens to his commander and makes a tactical retreat.
Isoc is not seen again until a cutscene sequence after Gate is defeated. The player character finds Isoc's body on the ground, and a slightly different scene plays out for each. If X defeated Gate, Alia informs him that Isoc's body is still functional, though he appears to be an empty shell similar to the Erasure incident in Mega Man Xtreme 2. If Zero defeated Gate, Zero hears a voice emanating near Isoc's body, telling Zero to proceed and saying he believes Zero is the strongest robot. Whichever happens, the character realizes they have no time to check up on Isoc, and he immediately leaves to go after Sigma. Isoc is not seen again for the rest of the game, and his fate is unknown.
- Like Serges in Mega Man X2, there is a prominent theory that Isoc is a robotic form of Dr. Wily. This is made evident by how Isoc is interested in Zero and hates X, and if Zero defeats High Max, Isoc will be pleased that Zero was able to defeat a robot X was not, and says he knows Zero inside out. In addition, when Zero finds his dead body, he hears a voice telling him he is the strongest robot.
- Also, Isoc's Japanese voice actor, Takeshi Aono, is the same actor that voiced Dr. Wily in Mega Man 8, Mega Man X4, and other games. Suetsugu's comment on how he was thinking about a certain scientist while designing him also supports this theory.
- Additionally, it should be noted that Isoc was capable of incapacitating Zero with little to no effort during the encounter that occurs after High Max's optional defeat. This is peculiar because Isoc's claim of knowing "Zero inside out", has massive merit. Never once did Isoc obtain Zero and analyze his anatomical structure, yet Isoc developed a method to easily subdue Zero and essentially paralyze his movement. To perform such a maneuver with no experience with Zero raises many questions, in addition to the fact that Zero still remained unanalyzable during this time.
- Branching off the theory of Serges being Wily, another prominent theory that exists suggests that Wily may be a stream of consciousness that transfers between different host bodies. This may explain how Serges was able to build a new body for Zero despite remaining unanalyzable, how Wily possibly built Sigma a body, and how Isoc possesses such knowledge of Zero to achieve immobilization. It should be noted that upon defeating Gate with Zero, a voice coming from Isoc's shell of a body, clearly labelled as "??" proceeds to call him the strongest robot. Furthermore, Isoc's body is clearly inactive, giving credibility that Wily is a stream of consciousness.
- Countering Wily's theory, it is also possible that Isoc was obsessed by Zero because he was impressed with the DNA data he and Gate managed to analyze. As he had never seen data so powerful before he began developing this specific obsession for Zero.
- However this might have been a act to hide his true identity.