The Goldfish of Doom

Silent and deadly.

"The teeth, I'll never forget the teeth!"

— Antonia Reyhan, the only hunter ever being able to capture a live specimen of this beast

While not technically a goldfish, nobody tells Chrysocetus Halipleumon Leaviathanos any other name than that - definitely not to its face because it would eat you before you'd get over the first syllable. This angler-fish like predator hides in the mud of shallow waters, near the edge of lakes and in large riverbeds. The only thing that is not hidden is a tiny antenna with a bright yellow end that glistens in the sun beams resembling a tiny goldfish swimming around anytime this monster flickers it about, to attract some fresh meal. It devours anything that gets close enough, unhinging its jaw and swallowing the prey whole and then sunking deeper into the waters to devour it in peace. The largest Chrysocetus specimen are able to swallow entire horses which they can feed of off for about a year.

"You think you'll be safe on land and that's the exact mistake it wants you to make."

— Antonia Reyhan, shortly after she killed the live specimen after it feasted on the scientists

Doomer as it is commonly referred to as well, is able to survive outside of water for about 30 minutes. Unlike common angler fish, it has several tentacles filled with paralyzing poison, similar to marine jellyfish, that it can use to move around. If all life surrounding a river or a lake gets more and more silent all of a sudden, it gives the fishermen an idea about what is going on. And those fishemer tend to find a new job or a new territory to fish very quickly until this beast goes back to hybernation or gets killed by a licensed beast hunter.

"Do you wish to die that bad?!"

— Antonia Reyhan, loosing her marbles after yet another expedition goes out to try to catch it

Trivia:
There is a famous urban legend about this creature kidnapping and eating people during rain and heavy storms. Particularly thieves.