Nightshriekers have a long, flowing tail of feathers and a long beak. Large, sweeping wings are used for aerial locomotion, and their long legs can run for a large distance. The "antlers" are in fact Nivali ornamentation.
Nightshriekers are carnivores, and have been known to eat other warriors on the battlefield.
The High Order of the Nivalis has trained these animals as steeds that can both run and fly. Their power was first demonstrated in a stealth strike on the Leseaw Empire.