The Nightshade Interceptor is an Eldar fighter aircraft and the vehicle of choice for the Crimson Hunter Aspect Warriors. This of course means that it is an exclusive aircraft for a certain Aspect. Why in Asuryan's name someone thought it was a good idea to make the Nightshade exclusive to a single division of Eldar rather than, you know, share it with everyone else to make it a full fledged fighter is currently a mystery.
The Nightshade represents the pinnacle of Eldar aeronautic ability. It is a high-speed craft designed to destroy any enemy fighter, even the advanced models of the Dark Eldar, meaning that it can function as both dedicated anti-vehicle and anti-aircraft support. And seeing as how it can keep up with Dark Eldar craft, it is quite impressive on its own. The Nightshade is most typically armed with two Bright Lances and a Pulse Laser.