Assuming you mean a Unity shader when you say "shader":
It doesn't have to be specifically for Spine but it does need to fit a few criteria, most of which are true for most Sprite shaders but not all.
Backface Culling is preferrably off, but this can be removed as a requirement in exchange for some some performance cost.
Depth Buffer/Z-buffer writing and reading is off. This can also be removed but you'll have frequent jagged edges visible. This will also potentially make sorting more problematic as the sorting will then (1) depend on more factors than just draw order via the engine's sorting system and (2) you have to juggle Z positions so the sprites don't become coplanar (or almost-coplanar) and cause z-fighting.
Lighting is not done through the deferred lighting because it will cause the lighting pass to overlap where the sprite pieces overlap. This is true even for SpriteRenderer. But if you have depth buffer on, this can work. The side effect of jagged-edges mentioned above will likewise apply.
AND
The premultiplied alpha setting of the shader needs to match the texture. More on that here: Premultiply Alpha
For this reason, if you packed your texture and it works with the Spine/Skeleton shader, you'll often get black edges with the built-in Sprites/Default shader. You just need to make sure you export with Premultiply alpha turned off whenever you want to use Sprites/Default.
I'm not sure which of these characteristics Magelight will fit in the end but it will likely affect what kind of shaders and sorting scheme you need to use.
