Please note that in this video the glow from Lum's esca does not grow when you collect planktids. This will change!
For those interested in the technique I used: it's really simple! I just attached a flat plane to each light source with a glowing sprite material. The material uses a Particles/Additive shader. Behind all this is another large plane with a semi-transparent black texture applied which darkens the background. The foreground rocks and creatures and all rendered in front of the glows so they are not obscured.
Happy New Year!