I'm thinking a mortal guardian of the Bible sent by God to save Gods word. Eli was blind but given a Godly sense of sight for his righteous journey, (I was blind but now I see)
I think Gary Oldmans character, the evil ruler of the small town was the devil's player. He was sending his demon riders out to rob,steal, even kill to find the "ONE" book to control all of mankind. Using it in a bad way.
Ironically in the end the devil was deceived by his captive woman and Eli being the only ones able to read braille. Both blind but had sight of the righteous path.
Eli was a messenger. savior and soldier of God.
"Even though I walk through the valley of the shadow of death"
After the end times event.
This movie was about the preservation of Gods word.