It was a nonsensical thing to say, for sure—but it was the first thing to pop into Nightmare's mind, and he had scrambled for anything to make Mal go away for even a moment.
When Jin spoke, he turned and growled, a sound like thunder. He could feel the demon beast on the other side freeze and boil at the same time.
"Nightmare?" The demon beast's voice was high and strained. "Why does it sound like I'm in the room with you, but I'm out here?"
Nightmare rolled his eyes, snarling out of desperation. "Go to sleep. You're sleepy."
"Please, Nightmare," Malphas said, sounding desperate. "This is incredibly dangerous! What if he tried to do something to you? Or me? I know it's hard for you but please, it'd be much safer if you took care of him right now! I'd even do it for you!"
He's using himself against me, Nightmare thought, and glanced to Jin again. "I have it handled. You needn't involve yourself. Go."
To his complete and utter surprise, Malphas did. After several seconds of trying to detect the demon beast, Nightmare relaxed. He could feel the full effects of the day's events on him; rest sounded more appealing than the entire universe right now.
What Nightmare didn't see was Mal standing at the corner of the hall, balling his fists and releasing them over and over. He'd been given an order...but was it wise to follow that order? Nightmare's fixation on these alternates would be detrimental in the long run. Didn't one of them say they wanted to destroy Nightmare? That was what Mal remembered.
He made up his mind. If Nightmare wouldn't look after himself, Malphas would. He strode down the hall, looking for a demon beast—any burly one would do.
Meanwhile, in the room, Nightmare addressed Jin. "You've...overstayed your welcome. You need to leave now."