As a demon from hell, I don't think lux is supposed to be near religious places/events. It looks like he's reverting back to his original demon form during a "holy" ceremony of matrimony.
That would only be the case if the couple had held the wedding at a church, which they didn't. Also, there hasn't been any reference to the relationship between demons and religion in this world.
As a demon from hell, I don't think lux is supposed to be near religious places/events. It looks like he's reverting back to his original demon form during a "holy" ceremony of matrimony.