Well, 2D or 3D? 2D is easier in some aspects. Here's how I'd do it: The orb would be 3D-rendered. A plain sphere, some bump mapping and a volumetric cloud-ish texture would probably work well. Any actual lightning coming out of it would be added with photoshop. The best way to do photoshop lightning is this: First do normal clouds and then difference clouds a lot with black&white. Then (I think this was needed) invert the colours and edit the white levels so that only the brightest white is visible.