Sparkfree is a changeling who has been put through the alicorn ascension process, giving her stronger magic and a much, much harder carapace than normal changelings. She serves as Celestia's zealous protector, being by her side during most outings.
Blitz Wind is the captain of the Regular Guard within Central Equestria. He's a mean, no-nonsense type who feels more than a little fed up with both the snooty upper class and the pack of youthful idiots he's legally obligated to refer to as his guards-in-training.
These two are a pair of my oldest pony characters. The very first picture of Blitz dates back to 2012, while Sparkfree arrived the following year.
Others in this series of ideas:
Dead Mares Walking