I finally got around to making some designs for the 4 guards accompanying Luna at the end of "MLSiaD: Nightmare Moon". Their names are based on the Greek gods that control the 4 directional winds. The two in the middle have designs I did not come up with (though I did make their cutie marks myself). You may recognize them from Luna Eclipsed in the show. That was the only time batponies ever showed up, and it was never officially stated what they were. The fandom went crazy with theories about batponies and made OCs left and right, but sadly nothing was ever done with them except Flutterbat and that was just Fluttershy being infected.

In MLSiaD, I decided to make batponies canon to my story. They are just another regular species of ponies that are nocturnal and keep to themselves in caves so not many know about them. There are some that live in the Everfree Forest called the "Cult of Eternal Night" who worship Nightmare Moon, but these guys are Luna's personal guard. In preparation for Luna's return, Celestia enlisted a platoon of batpony guards to protect and assist her at night. These four appear at the end of the story and help fight against the Ram Golem.

Here are some quick bios for them:

Boreas - the captain of the guard and a very experienced veteran in Celestia's army. He is firm and serious and takes his job very seriously. Keeps his troops in line and is very protective of Luna.

Notus and Eurus - twins that started off as trainees for Celestia, doing guard duty at night. They accompany Luna to Ponyville and are usually pulling her chariot. Notus is the more brash and coldblooded while Eurus is down to earth and friendly.

Zephyrus - one of the younger guards, but very eager to meet the Princess of the Night and prove himself. He is a big-headed and sometimes gets himself in danger, but still an excellent soldier. He and Noctura have romantic feelings for one another.

There you go. I might do some proper bio cards for them someday and I have a large image of all the characters from the Nightmare Moon Arc that will release soon so stay tuned!