I think råder is perhaps used in the book to make it sound more historic, I am not sure, but I think it used to be more common. Another example that pops up in my mind is the song "midnatt råder", midnight... pervails? So that is one way to translate it, and that song might be old enough, or might try to sound older than it is, by using råder as well as the old plural verbform that is out of use. So I'd use råder sparsely in modern language, except possibly in formal and institutional language. Råder can also be a verb though "jag råder dig att..." I advice you to...
I think "finns" is more like is or exist, and råder a bit like exist, but also perveils, and has a tint of... authority about it, that it is the somethin incharge at the moment, be it night instead of day or a state of lawlessness instead of peace. I think the word is related to rå and råd, the first a spirit being in charge of and caring for a part of nature, and the second a council, deciding over something, both of which "råder" over their respective spheres.