Perhaps it was the same light that bathes the tree.

[Her lips form a thin line, she's speculating about its nature and what it means.]

I do as well, though it seems it will be difficult. They could be in another level of the tree we do not have access, for example, or on the other side of the bounded field made of mist beyond the branches and the roots.

[She wants to know too, the animals can cross the fog freely, according to Korra, why couldn't they?]