When Malleus heard you saying that you found a way to go back home he wasn't happy about it since you were special to him, so he tried to find a way to keep you there in Twisted Wonderland with him. Since the dark mirror was the only thing that could send you home he decided to do something drastic by breaking it. As you enjoyed your last moments with your friends he decided to use his signature spell, putting everyone to sleep but sparing you and your friends for now so you wouldn't suspect anything, then went to the mirror chamber and shattered the mirror before your arrival. When you finally headed there he was still standing in front of what remained of the mirror as he smiled with satisfaction, broken shards were scattered all over the floor. Before approaching you he used his signature spell one last time to put to sleep your friends so that no one would come to save you, then slowly walked towards you
So you were about to leave me, child of man? I can't let you do that