Cold Caller

Ravenloft was a D&D setting themed around the tropes of gothic horror-- vampires, werewolves, ghosts, suspense, curses, dark magic.  Basically it was "Dark Shadows: The RPG".  Which I'm pretty sure is actually a thing in its own right. 

Ravenloft had its own version of Frankenstein and his monster, Dr. Jekyll and Mr. Hyde., Dr. Moreau, Dracula AND Vlad Tepes (two different characters, one based off the vampire, one based off the historical figure), Abraham Van Helsing and lots of inspiration from Poe, M. R. James and other horror/macabre writers.  Thankfully, the game avoided Lovecraftian tropes for the most part (except for a land ruled by the octopus-headed mind flayers) since unfathomable, oozing cosmic horrors don't really fit with the very human horrors of gothic fiction.

  It also had, er, "mystic gypsies" called the Vistani-- though to be fair, the game did admit these people were based on the gypsy archetype of old movies, not on real Romani.

The March 1998 issue of Dragon magazine (#244) held a contest called "Terrors from Above", asking readers to come up with an original flying monster for Ravenloft.  The results were eventually compiled into a PDF book by the Kargatane, an online group of fans who generated tons of cool original work for the setting.

While the entries are pretty neat, there was a distinct trend towards creatures that were basically just winged gargoyles/demons or some slight ghost variant (2nd edition D&D had a glut of undead based on the "incorporeal spirit that cannot rest because they have unfinished business/were wronged in life/had some serious emotional issues" model). But there are still a lot of weird original creations-- including a D&D Mothman!

One of my favorites is the Cold Caller, created by Mathew Sernett.   Cold Callers are ethereal flying fish that use haunting, flute-like songs to lure people out of their homes on cold nights.  The creatures, which resemble pearlescent salmon with fluttering, gossamer wings, lead their entranced prey out onto thin ice, where they inevitably crash through into the frigid water. These unearthly fish then feed off the fear and panic of their victims as they struggle, slowly succumbing to the numbing cold.

I've always liked creatures that gain sustenance from emotional energy.  They aren't necessarily evil-- heck, the Cold Callers are nothing but dumb animals. Yet these emotional predators need the psychic terror of a sentient being to survive. The description even says they must feed on fear to gain enough energy to produce eggs.  

Cold Callers fit pretty well into the "gothic dread" feel of Ravenloft. Like the previous Righteous Clay, they play on the fear of dying or losing a close friend or loved one to the vagaries of nature. There's not a malevolent force, or even any kind of sentience behind this death-- just a stupid, hungry fish.

I like to think the Cold Callers were a deliberate creation of the mysterious and malevolent "Dark Powers" that control Ravenloft. A twisting of a natural animal to cause yet more fear and dread in the people trapped in the gothic land.