He brushed aside that particular thought as Twilight began to speak. "Once the Tantabus infects a dreamer, their dream changes into a nightmare. Allowing the parasite to feed on the negative emotions and gain power. The more dreamers it infects, the faster it can do so. Once it has enough power, Princess Luna thinks it will be able to escape from the dream realm into the real world and turn all of Equestria into one massive, never-ending nightmare!"