Artist’s description from Deviantart:

The Mountain Pegasi are the closest living relatives to the old purebred pegasi. 

This sub-species only exist in one place and that is the tropical montains in the outskirts of the dragon lands, far away from Equestria. 

Only a few exist as there is only one large town high up in the mountains that exists. They build their houses inside of the mountains, making structures and tunnel systems that can’t be detected from the outside. They also use clouds as platforms and roads outside of these mountain openings. The clouds are usually place for things such as weapon training, flying obstacle courses and more. 

These Pegasi are a warrior people, praising the strong and the fearless who have proven themselves in battle. They do have a group that governs the internal things in their society yet the highest respected pony is the General. In this case it is General Valor (pictured above) 

Because of the fact that they live so close to the majority of the dragon population they often need to fight of giant reptilian intruders. And since none of them are afraid of getting violent most pegasi have scars somewhere on their body from these vicious fights.  

They are extremely wary and not fond of strangers. 

Living right above the tropical jungles they often send foraging teams out to collect food.

These pegasi are slightly bigger than your average pegasus from Equestria. They have larger chests and stronger front legs as well. They are also much more feathered, with feathers covering about two thirds of their bodies opposed to just the wings and neck. Their wings are bigger and they also have very prominent colors on the insides of their wings. They have shorter and rounder muzzles than their relatives too.  

Males are usually more pointy and stockier than the females.

They are usually very colorfull and some strike resemblance to tropical birds. It is very rare that they don’t have any streaks in their mane. 

They do not have the ability to control the weather, like making clouds rain or shoot lightning. But they can manipulate and sculpt clouds in different ways. 

These ponies are mere legends in Equestria and few ponies actually believe they exist (Dragon fighting, super pegasi? Who would believe that?)