Defeat the Goblin on the Overpass

Travis is gonna cast shield of faith around around Magnus okay can you explain what that does shield of faith shimmering field appears and surrounds creature of your choice within range granting it a plus two bonus to AC for the duration. The order moves to the goblin on the overpass he sees you put a magic beautiful shield around this already heavily shielded fighter in the front so he sort of turns his attention off of Magnus he's pretty sure he can't penetrate all that. He rolls a oh Jesus a 21 versus AC what's your armor class 18 18 so 21 beats your 18 so he hits you four okay four plus two so six piercing damage okay I'm going to cast ray of frost on that fool