After the fall of Princess Luna and the banishment of Nightmare Moon, the Lunar Guard comprised of the Thestrals ("Bat Ponies") stayed in the area of Equestria known as "Hollow Shades", south of 'Neighagra Falls'. In those thousand years the citizens stayed out of Celestia's sight, figuratively and literally; preserving thier culture, families and the history of their princess; waiting for the day she would return to lead them again.
Growing up, Icarus was otherwise a 'normal' and otherwise unremarkable Thestral; he trained in the military arts hoping he would live to see the day Luna would come home.
Now in his early 30's (eqiv age), his community now no longer hiding in the near twilight / night of The Shades, he finds himself a little overwhelmed with the changes in Equestria and the Thestral's position in society.
His cutie mark is based on his own comment one that he would one day, "...fly around Luna's Moon and back again!", showing his dual-colour'd tail streak launching around the back side of The Mare in the Moon. His tallent is being a High Flier, able to launch himself from the ground HIGH and FAST, with speed to rival most determined pegasi. His wings are able to gather more lift and deal with the colder/thinner air for longer periods of glide-time, making him good for survalence & high-priority deliveries where magic cannot cope.
(His cutie mark is based on the Real World Apollo 8 Mission patch, showing a free-return orbit of the capsule around the Moon and returning to Earth.)
He's mostly aloof, raises his left eyebrow a lot to show annoyance and curiosity (a la Spock), will protect the tiniest foal from harm or injustice and brush it off as 'Just doing his job'. He's single, not willing to commit to anyone, but happy enough to spend time with mares from time-to-time.
