The Cobra is one of the three super-heavy skimmers of the Eldar, the others being the Scorpion and the Lynx. Apparently, in Eldar mythology, the cobra was the brother of the serpent but a short-tempered, fickle ally, to whom the serpent turned to for aid only during the darkest days of the War in Heaven. The Cobra is an Engine of Vaul, much like it's counterpart, the Scorpion, but re-armed with a large Distortion Cannon (D-Cannon) called a D-Inpailer. The Cobra is best compared to the Shadowsword, a titan killer that uses its D-Inpailer to rip large chunks of the enemy into the void.
There are two versions of the Cobra. Type I has a turret-mounted D-Cannon, while the Type II has a fixed forward firing D-Cannon. The one you see here is the Type II version of the Cobra super-heavy tank.
As with all Eldar vehicles, crew numbers are kept to a minimum. The dwindling civilization of the Eldar means they must rely upon sophisticated technology and the Wraithbone construction of their vehicles, freeing more warriors from crewman duties to fill the ranks of Guardian and Aspect Warriors squads.
The Cobra uses the same chassis as the Scorpion; this means that the super-heavies of the Eldar are stupidly fast and agile both in fluff-terms and on the tabletop. Other than its stupidly humongous D-cannon which makes even void shields collapse on themselves like wet tissue paper, the Cobra also comes equipped with a titan-grade Holo-field as well as secondary armaments such as a Bright Lance, Eldar Missile Launcher, Scatter Cannon, Shuriken Cannon or Starcannon. Some Cobras are also upgraded to include Star Engines and/or Vectored Engines for improved handling and speed.