The source of Cadence's pain became pretty obvious as Celestia and Luna returned to the city entrance. Faust was there, her horn ablaze as she cast a beam directly at the shield that threatened to burn through it. Luna didn't need to be creating the shield to know that it was rapidly failing. The Heart fed on love, and in its current state, Canterlot wasn't exactly brimming with such emotions, and neither was Cadence herself. Luna wasn't sure whether she should be scared for Cadence, or of her.