I wouldn't know that I'd be good at analysing the lyrics and since I tend to bend the meanings to my own personal interpretation, regardless of the original writer's intention, I doubt that many here would agree with my analysis.
The best lyrics, IMO, are open to many interpretations. This thread is about sharing them.
I still don't have a firm handle on Shadows, but I did some googling.
Apparently ravens were were marked out as method of foretelling in ancient Celtic culture, but I'm sticking with the premise this song is based on biblical references.
Into the Valley of Death fear no evil is a reference to Psalm 23:4, which basically about how faith in God will carry people through the darkest depths of their lives.
The raven's call fits in the sense that Psalm 137 states "Consider the Ravens. They do not sow or reap; they have no storeroom or barn, yet God feeds them - another reference to faith.
The firstborn of all men will die - like in Exodus, except for the firstborn of the faithful Jews, who God protected.
The wayward child is the Prodigal son, one God loves despite his straying.
The opening section can easily be interpreted as being about faith - soulless, aimless nightmares grow in a world without sunlight (faith)
Look for guidance from the one who knows (God?) In the book that he wrote (the Bible?)
The chorus could be saying "be open, honest, free and faithful, mourn the fallen and you will outlast them."
The whole song could be all a metaphor for staying true to your guns, trust what you believe in and it will carry you through the dark times. Fits with what we know of Steve's character. Or Steve may have actually found Christian faith later in life.