Chemical eel Monopterus albus, similar to Erlang God. It is fierce and violent. The appearance is similar to that of ordinary Monopterus albus, and the volume is slightly larger. People who bite will melt even their bones.
Of course, this is just a legend. When I was young, old people often told these stories. The purpose is to prevent children from catching Monopterus albus in rivers or fields to avoid drowning.