I think it would be interesting if it interacted with mirages other abilities. Sleight of Hand could create an area of shadow, Prism could fill the room with light! Or maybe make it that tapping Sleight of hand creates an area of shadow, and holding it creates an area of light.
If that's not possible, I'd say make it a toggle, and nerf the helminth version. The main reason I never use Mirage or subsumed Eclipse, is because the ability is very unreliable.