Premise

Every world needs a theme; a thing that defines the world and the way it interacts with stuff. Some of the better themes are contrasts such as good and evil, order and chaos, or nature and science.

This is a world of Light and Darkness.
Not good and evil, as neither side is especially good and neither is especially evil. A peasant is as likely to be cut down by a wandering warrior under a noon sun as he is to be eaten by a terror of the moonless night. His chances of being rescued from an accident in the woods are equally divided between another human trying to help him and a benign creature of the dark.

There is no normal lunar cycle. The moon of this world has such an orbit that it is only visible four or five nights a year. It is often visible during the daytime and is commonly believed to be the spouse or child (still undecided on that) of the sun.

Magic is real but it is literally a thing of darkness. To this world, the absence of light implies magic in the same way that being alive implies respiration. The two are so closely tied together that it is very difficult to separate the two conceptually, and practically impossible to separate them in fact.
A side effect of this nature is that magic becomes unstable in the presence of light and impossible without some darkness, such as strong shadows. Also, magic can not generate any sort of light source; no magical fires, no dancing lights, nothing like that can be accomplished.

That's enough for now.