Humiliation was the most Prudence would get in this situation. Lantis thought that it was the most that could be inflicted on her—on them as part of her acquaintance. He really didn't think that those two people spared from his magic would deal the biggest damage to them tonight. Alexander Reed and Melissa Sanders were just two pieces of human flesh.
Yet, they were enough for the phone to explode in demon magic and make Norghasta act without care toward June or any other human around him—not even toward him, Lucirien.
That was why when the two vanished in that dim dining hall, Lantis decided to tap into his anger and kill everyone else around them. No witnesses would mean no lips to tell what happened. However, in an instant, a blinding light ate everything in sight. At Belledel's intervention, Lucirien only transported everyone from Perseus away from the place.