This Nightmare featured in Chapter 1 of the Dungeons & Dragons campaign: War of the Triplets.
This mini was fun to paint, but it was a back-up mini in the game if things went wrong. Essentially the party was to save a Unicorn from being sacrificed in a evil ritual to create a Nightmare.
Fortunately for the unicorn the players managed to stop the ritual, but that meant the Nightmare didn’t get to take the stage…. this time!
As you may have noticed there’s a burning horse corpse as well. This was used by a mock Necromancer to create diversion to trick the players to think the Unicorn was already dead to make them give up on finding the Unicorn.