You can find out detailed descriptions of all the characters at the following link. http://www.enotes.com/bronze-bow/characters
Daniel, Joel, and Malthace take an oath in which they vow till fight and kill the Romans. Their sign for secret communication is the Bronze bow from taken from Psalm 18:34.
He trains my hands for battle;
my arms can bend a bow of bronze.
A Bronze Bow is an impossible bow to bend. When Daniel Joel and Malthace take an Oath to fight the Romans together, they use the Bow as a sign because they believe that their Oath, like a Bronze Bow will be impossible to bend or break. Nothing can force them to give up on each other and break that oath. What they do not count on is Jesus. He shows them that love can make them break their oath: only love can bend the Bronze Bow.
He is a cool guy