It's the indestructible, yet somehow shapable/cuttable stuff they made the hull out of in The Core. Just as nonsensically magical as Doonium. (I think someone may have been reading McCaffrey while writing that technobabble guide.)

__________________
[Dr. Horrible]___________________________[Penny]
Listen close to everybody's heart________And you believe there's good in everybody's heart
And hear that breaking sound_____________Keep it safe and sound
Hopes and dreams are shattering apart____With hope you can do your part
And crashing to the ground_______________To turn a life around