This is the basic idea to making a Nightwing. First you will need to get some shapes cut from plasticard as shown below. You're also going to need a Wave Serpent kit (or the parts from that kit) for the engines, cockpit, glass canopy, and weaponry. Any Eldar tank will do if you have spare weapons though.
Start by cutting out the shapes required on plasticard, like below.
Eldar Nightwing Scratchbuild – Part 1
by Akenseth | Feb 9, 2012