Nyx

'Nyx' is a black alicorn filly who first appears in a minor role in Pen Stroke's fan fiction work Creeping Darkness and is later a major character in Past Sins, Nightmare or Nyx?, Trinkets, Winter Bells, and First Hours'' (written by the same author). In the first story, she is Luna cursed to take the form of Nightmare Moon as a foal. In the Past Sins series, she is Nightmare Moon resurrected as a filly. Pen Stroke stated that all authors could use Nyx or any of his characters as long as the writer respects the characters, does not use overly mature themes on the characters, and gives credit to him for creating the characters.

Trivia

 * Nyx is best friends with the Cutie Mark Crusaders and Snowdrop's direct descendant, Snow Pillow, the daughter of Queen Frostine.
 * Nyx will appear in The Inquisitor's Revenge Part 1, and she'll be adopted by Prince Flash Sentry and Princess Twilight Sparkle in The Inquisitor's Revenge Part 2
 * Nyx will meet Team Robot someday in near future.
 * Nyx also appeared in Princess Twivine Rises!, and throughout with Skyla, Yuna, Snowdrop, and the gang in Thomas, Twilight, Brian Griffin, and friends' Amazing Escapades.