Voidborn Quinn (Legendary skin concept)
Concept: Quinn would likely reflect a grotesque humanoid figure, I imagine Quinn's model using hind legs that reflect that of a bird while also incorporating the idea of digitigrade walking animations (animals that stand or walk on their toes). Her arms would be thin to the bone with a sunken body composition overall (think visible ribs, waist similar to old Morgana's splash art). Of course this is all accompanied by the Void's purple color palette. One of her arms could be merged with her crossbow, with a flap that shoots a projectile out of her body. Her head only consists of a lower jaw and a singular empty eye socket.
At level 6: Valor would be replaced with a Voidborn parasite (Voidborn are Runeterran beings constructed by the Watchers of The Void. Their reason for existing is to accept, consume, and learn all the information about Runeterra necessary enough to aid for the eventual return of the Watchers.) Incorporating the concept of the watchers, i thought having Valor behave as an eye during Quinn's ultimate and completing the upper half of her body would make for an interesting void skin. (2 halfs, with the other coming into play throughout and merging with her head at certain times. Valor (Voidborn parasite) herself would also appear as mostly a grotesque winged eyeball (basic idea) that grants Quinn "vision" throughout her W and passive animations, and guiding her during her R. Instead of coming from the air, I thought during her animation when Valor picks her up, the bird would instead emerge from within her body due to the parasitic nature, almost as if hitting lvl 6 is the wake up call to take control. Her projectiles would be similar looking to Kaisa's plasma when she lands or autos. In addition a voice over to match the equally grotesque depiction (possibly a more "one of us" approach as the lore behind this skin is Quinn being overtaken by the Voidborn with the only goal that is serving the Watchers.