Nessie

Stretching roughly three and a half meters, Nessie took the form of a water-dwelling reptile shaped much like a plesiosaur, with a slender neck, a bulky middle, a tapering tail, and four strong flippers that drove it through the water. Ridges and lumps studded its head, and its tiny white eyes held black, sharp pupils. The jaws hid rows of uneven teeth around a tongue split at its end, and could gape wide to launch its signature attack. Striped, lined markings covered its body beneath a crest along the spine, while two pairs of unusually long gills ran each flank from just past the head down to the tail.

Nessie behaved like a wild beast, lashing out at anything it noticed or simply sensed nearby. Although it answered to the Serpo on paper, the creature lacked the wits to grasp or carry out commands, so even its supposed masters got caught up in its indiscriminate rampaging.

Sightings of the creature reportedly stretched back to 700 AD, but it became famous in 1934 when a London obstetrician photographed it at Loch Ness in Scotland, cementing its reputation as the Loch Ness Monster. That so-called surgeon's photograph convinced some of its existence while many dismissed it as a fake, and later speculation floated the idea that the animal was really a giant eel.

During the Serpo Arc, the aliens hunting Okarun for his Turbo Granny power brought Nessie and a hired Dover Demon to seize him at school. Prowling the halls, Nessie nearly catches Momo, who hides until a stray noise gives her away, prompting a high-pressure water blast that wrecks a classroom but narrowly misses her. It resurfaces later to flood the Serpo's confrontation with Okarun, Aira, and Momo. With Nessie too uncontrollable to direct, a surviving Serpo fuses itself with both the cryptid and the Dover Demon into the Serpo Dover Demon Nessie as a final gambit, but Okarun shatters the combined body and kills Nessie in the process.