Novuzeit recently released Neon Black, which contained a puzzle. Upon solving this puzzle (which Mark Piotrowski did) the Nightmare Machine would be unleashed.
This plug-in was supposedly the last DarkWare plug-in ever made, but it was never released so people wondered if it was actually real. You can read more about this story here.
The Nightmare Machine is still beta (and will stay that way) and contains at least one bug. From the included readme: If the audio goes completely to the right channel, play with the reverb knob to get things back to normal.
Also note that this thing can get nasty loud, so mind your ears and equipment.
Visit the DarkWare site for more information and a link to download the Nightmare Machine.
