Light and Dark are usually stand-ins for Good and Evil. Hence the winged warriors or Angels. In story terms, you have the avatars, chosen ones or champions of the gods or whatever protagonists and antagonists you wanna have.
When first reading your post, I did not immediatly think of warriors. You could also bring knowledge or literal light to a dark kingdom.
But then you jumped to the generic good hero will fight against the big bad trope. Nothing bad there in tropes, but I had the impression you want to try something seldom seen or unique.
If you wanna go abstract, your protagonist could be a thought or the beginning of a thought that has to enlighten the whole brain from boredom, stagnation, sleep, death by fireing up the neurons to activity, experience, wakeness, life.
The gist of your story would also be applicable to what is written in several religious texts. How the chosen of god has to spread the word anew.
Or to put it bluntly, dark vs light is as universal as boy meets girl in terms of starting point for a story ;-)