Gwoemul

Gwoemul was a large amphibious predator mutated from an unknown organism (though it has been mentioned by some to be a Tadpole, but this has not been confirmed) by various pollutants in the Han River. It was an extremely aggressive and dangerous creature that would often hunt humans near the river, bringing them back to its lair in the sewers. It was afraid of fire; ultimately it died after being set on fire.