I had just assumed that the Wandering Light made enough light to illuminate a great deal of the Terra Firma, as well as the bottom sides of the Wanderers.
Apparently in the description a portion of his avatar does emit some glow, but considering how it is described, I'm going to call it as having roughly the equivalent output of half that of what the Earth's moon reflects. You can see the source and some other things, but not very well.
Unless Wolf made the trees like Mallorn trees, which produce their own light.
Didn't specify, so that variant does not exist. Really, the light problem is significant to Wolf. On the previous turn, the trees were supported by the godly power that made them, but that is waning fast and they will be relying upon natural processes, and without any light...
Hey, Zanzetkuken. Would one need a Mighty Act to create a small sun which would orbit around the planets?
Yes, but I'll call it as one Mighty Act for 3 (relatively) small sources, one for each planet.
Next question. Can I mess with the acts of others during the turn in which they were created.
You know what, I'm going to assume you can't and do something else instead.
Actually, you can. Just try to make it subtle so the other god doesn't notice. Gods aren't omnipresent or omniscient, but they are a lot higher up there in understanding than any mortal can achieve, so the unnoticeable falls closer to slight behavioral modifications, a slow degradation (>10 turns) of the creation, or other minor act shenanigans.