from March’s Creatures Beyond the Walle

Unlike other magical creatures, nightmara do not live north of the Walle; thirteen large herds live in Calatini on the plains just north of the Tsarkan Empire (dubbed the Nightmara Plains), and a few smaller herds live in other human nations. Nightmara live among humans because they must consume dreams in addition to ordinary feed, and humans possess much richer dreams than other creatures. If nightmara do not consume enough rich dreams, they develop dreamsickness, becoming feeble and fatigued.

In size and shape, nightmara appear similar to horses. Their coat and eyes are always shades of black, taupe, or midnight, and their coats may be dappled in those dark hues. At night, the edge of nightmara seem to fade into darkness.

Although they appear similar to horses, nightmara are far superior and cannot interbreed with them. Since nightmara consume dreams, they eat much less ordinary feed and can survive on rougher fare like goats. They also possess human intelligence and lifespans, and once their loyalty is earned, they remain loyal until death.

These traits inspired humans to attempt to enslave nightmara by killing dames and stealing their foals. These attempts usually failed because foals raised by humans did not receive proper training, and their powers were uncontrolled at maturity, causing them to drive nearby humans mad or into comas.

Because of this negative cycle, Nightwind, a wise nightmara queen in the seventh century, decided to form a treaty with Calatini. Signed again every twenty-five years, the Nightmara-Calatini Treaty has protected human and nightmara alike for nearly four centuries and is one of the unique aspects of Calatini.

Nightmara live in herds led by dominant mares, and the strongest of these mares is the nightmara queen. The nightmara queen and dominant mares are not determined by their lineage but by their power over dreams and the mind. They use this power to control the herd, even forcing them into a dream state during emergencies.

Nightmara communicate using their thoughts. Unlike other magical creatures, like griffins, who do the same, nightmara can communicate to anyone they choose rather than just those able to hear thoughts. This ability has allowed the nightmara herds to closely bond with the mara clans, humans sent to guard the nightmara as part of the Nightmara-Calatini Treaty.