Pegasus ponies (singular: "pegasus", plural: "pegasi") are a race of pony that have the unique ability to fly and magically control the weather. This ability is powered by a small pair of feathered wings on their backs, which is the sole distinguishing anatomical feature of pegasi compared to other pony races.
Before the War
Pegasus Ponies are normally associated with control of the weather. They are the only pony able to interact with clouds as if they were tangible, allowing them to disperse clouds for extra sunlight or gather clouds for various forms or precipitation. Most pegasus buildings and homes are made of pure cloud.
During the War
Air Superiority has long dictated who was most successful on the battleground. Much like the cavalry of human ground warfare would be the deciding edge in an engagement, so too was the appearance of pegasus. Fighting could be done at a distance and from high elevation when pairing a pegasus with a battle saddle. Pegasus ponies were also able to tow battle carriages. Late in the war they received power armor similar to the Steel Rangers.
Many pegasi felt that the war between ponies and zebras should be left with the earthbound races, as more and more battles called on greater numbers of pegasi to fight and die. In their mind, the conflict simply did not involve pegasi.
After the War
In spite of the isolationist view held by the majority of pegasi, Cloudsdale was the first city to be hit by a megaspell strike. The strike was such that Cloudsdale ceased to exist, the city being such a high value target due to the lethality of pegasi in the war. This event steeled the resolve of the greater, surviving, pegasus community to seal themselves off from the world below the clouds. Dissenters who ventured below for any reason not sanctioned by the Pegasus Enclave were literally branded as traitors, scarring over the natural cutie mark of the offending pegasus with a depiction of Rainbow Dash's cloud and thunderbolt. Rainbow Dash had been the first pegasus to return to the surface, and all pegasi that have done so since have been called Dashites.