Just from reading the OP, my view is:
- I disagree with the idea that it was the entirety of Solus' light output. From context, it seemed like it was referring to all the light hitting that area of the planet. That's just how people talk about stuff like that. I think the comparison to an eclipse actually supports this; eclipses on Earth only involve a spot across the planet's surface being darkened.
- I'm a bit unsure about the general applicability of this; it was explicitly not generating heat, and it seems to have killed monsters which, from that little context, read like they could very well be weak to light. Especially given how no notable effects on the environment were mentioned, aside from it hurting some people's eyes.
And so, I'd want it indexed as "{whatever tier that amount of light hitting an area the size of that forest is} with Light Manipulation", which within matches can be used to absorb that much light from the environment/opponent, and use it to hurt their eyes or dispel constructs made of darkness, or that are otherwise weak to light.
Note that these, especially the bit about applicability, could easily change with more context I'm not aware of.