Sludge Villain

The Sludge Villain is opportunistic, violent, selfish, and primarily concerned with escaping capture.

He treats other people as tools. When he encounters Izuku, he attempts to enter the boy's body and use him as a disguise and means of escape, showing little concern for whether the process will kill his victim.

His behavior toward Bakugou is similarly practical. Once he realizes that Bakugou possesses an exceptionally destructive Quirk, he views the teenager not merely as a hiding place but as a potentially powerful new body.

He lacks the ideological motivations associated with later villain groups and is fundamentally presented as a conventional criminal driven by survival and self-interest.

The Sludge Villain's unnamed Quirk transforms his entire body into a viscous mud-like substance. Conventional punches and restraints are largely ineffective because physical force simply displaces portions of his fluid body.

He can envelop another person, enter their airways, and attempt to take control of their body. Successful possession also allows him to exploit the host's Quirk.

While controlling Bakugou, he gains access to Explosion and becomes substantially more dangerous because the destructive blasts compensate for his own limited offensive range.

Strong air pressure can scatter his fluid body, making powerful wind-producing attacks particularly effective. Later material also demonstrates that acid can disrupt his sludge form.

The Sludge Villain encounters Izuku shortly after escaping from All Might. He attempts to possess the Quirkless teenager before All Might intervenes and captures him.

A mistake allows the villain to escape again, after which he encounters Bakugou and attempts to seize his body.

Several professional heroes are unable to safely resolve the hostage situation because their Quirks are poorly suited to separating a liquid villain from a trapped child.

Izuku nevertheless runs toward Bakugou instinctively despite possessing no useful power. His action pushes All Might to intervene despite his physical limits, and the resulting rescue becomes one of the defining moments leading All Might to choose Izuku as his successor.

Much later, the Sludge Villain resurfaces amid the national conflict and becomes associated with the Paranormal Liberation Front's scattered forces.

Izuku Midoriya becomes the Sludge Villain's first attempted host and later recklessly rushes to stop him from suffocating Bakugou.

Katsuki Bakugou is the host whose Explosion Quirk makes the villain substantially more dangerous.

All Might captures the Sludge Villain twice and ultimately defeats him with a powerful air-pressure attack.

Death Arms is among the Pro Heroes unable to safely separate the villain from Bakugou during the hostage crisis.