The Shadow Mare

The Shadow Mare is

and the main antagonist of the fifth season of My Little Pony: Masters of Harmony. Her previous intent was stealing the Alicorn magic from Princess Celestia, Princess Luna, Princess Cadance, and Twilight Sparkle to take over Equestria but when she viewed Tirek doing it from Limbo, she lost it and wanted to destroy the Princesses instead.

Bio
The Shadow Mare