Simple blade material; jack up the
ambient value until the blade looks right:
The emitter should be the same color, but with considerably ambient value. Adjust this value so that the strength of light cast looks right; ignore the appearance of the emitter itself, since you'll only see the light it casts onto surrounding objects and not see the emitter itself.
The glow aura "halo" effect is gained by daisy-chaining two edge_blend nodes. Feel free to adjust
ambient value and the
attenuation of the edge_blend nodes.
To render in P9+ Firefly, engage
indirect light, set
irradiance caching and
indirect light quality to about 70, and give it 3 (or more)
raytrace bounces. Be generous with the
pixel samples. In P11, you set pixel samples to 100 and use progressive mode and cancel the render when it is satisfactory.
demo renders:
Caveat: If viewed in reflection or through a refractive surface, the emitter will be visible.
You can text-edit the emitter PP2 prop file and set visible in reflection to 0, if that's within your skill set. I have no solution to offer for cases where the emitter is seen through a refractive surface, other than to avoid it.