He looked at his dead parents and the light in his eyes dimmed. Then he looked at the masked guy. He knew that his parents have been assassinated in their sleep inside a fort on the frontlines. He had never seen it in person but he had imagined how it might have happened and this scene around him is almost the exact representation of that.
Is this how the Nightmare spell works? Vishnu thought for a bit but quickly placed his attention on the masked figure. He had never found out who is exactly the guy who assassinated his parents. When he tortured the king of the Enemy kindom he learned that they've already killed the killer to leave no evidence of their work and Vishnu could confirm that as he didn't believe that this king could lie in the face of his torture and he has no reason to.