It's understandable, but it comes over as a very literary form (which might be what you want), for two reasons.
First, "Neither .. nor" can coordinate many different grammatical constructs: noun phrases (I drink neither tea nor coffee.), verb phrases (I neither want nor expect your thanks) and complete predicates (I neither watched TV nor went to the park), but it doesn't usually coordinate whole sentences, as in your example. It can do, but it's uncommon in ordinary speech, and feels literary.
Secondly, when "neither" does stand first in a clause in this way, it tends to behave like other negative-polarity terms, and trigger inversion:
Scarcely had he left the room ... (not Scarcely he had left the room ...)
Never could I imagine that! (not Never I could imagine that!)
So your example would more commonly be
Neither does light expose him, nor does darkness hide him.
This is a tendency, so what you have said is not ungrammatical in the way that Never I could imagine that! would be; but to me it makes it very literary, almost archaic. It does sound better in a poetic sense, though.
Nor
should not be capitalised, it looks fine to me.