Brock, Starfield Guide

This card's cost is reduced by one mana for each
devotion of that color.
(Each {w} in the mana costs of permanents you
control counts toward your devotion to white.)
Your enchantments cost {w}{u}{b}{r}{g} less for
each devotion to that spell's color.
(If your devotion to blue is 2, the spell cost {u}{u} less.)
"Believing is Seeing" ~Brock, Starfield Guide