Alcestus

The natural world faces many dangers, from the axes of humanoids, to rampaging outsiders. Fortunately for all there are just as many defenders who rise to defend the wilds. Alcesti are one example of such.
These defenders are formed from large herbivores with celestial ancestry. They keep their form, but with wings and large antlers.

In combat an Alcestus strikes telling blows with hoofs and antlers. Beams of force strike form their antlers, both defending from arrows and striking unerringly at enemies.

They usually live among herds of their kind, but when their environment is in danger they move to strike against it. Both this and the value of their antlers for the creation of magical items lead them to be hunted by many.
For those living peacefully in or near the roaming grounds of alcesti often see them as messagers of the gods, and on occasion alcesti do indeed serve as such. 

It is said that great champions of nature are at times presented an alcestus as companion and mount.

CR: 5
NG Large Magical Beast
Combat Role: All-rounder, ally

Thunder Rolling Along the Plains is the great horse spirit who guards the vast savannas in the center of Behisris. His hoofsoldiers are celestial horses with wings of grass and antlers of wood.

The Count of South-Belgrad has invited nobles from far and white for a great hunt. The greatest prize is a large hind with golden antlers that has been spotted in the count’s lands. In truth however the count uses the hunt as a way to get rid of the Alcestus that has been blocking his attempts to turn an ancient forest into farmlands.

As the party is traveling through dense woodlands they see a strange animal. It looks a bit like a brown horse or deer, but with striped legs and crystalline antlers. They keep seeing the animal, and it looks like it wants to lead them somewhere.

Monsters of Porphyra 3 p. 18