The Heart of Darkness, also known as the Thuviskaroth of Cataphylaxis and Orb of Power is a powerful black crystal and an artifact featured in the Iron Man comics. It made its first appearance in Iron Man #309.
It is an orb of apparently mystic energy; the alien Century believes it is an ancient artifact which acts as a "lens" to attract and focus all manner of dark power. The Mandarin uses its power to turn back time in China, and literally transforms it into a feudal nation again, one in which electronic equipment cannot not operate. Iron Man, with his team Force Works and ally War Machine defeat him, but not before the Mandarin discovers that Tony Stark is the man inside the Iron Man armor.
Iron Man infects the Mandarin with a techno-organic virus, and the Heart, seeing him infected with technology, rejects the Mandarin and implodes. Iron Man believes him dead, though in reality the Mandarin has been transported and transformed, by the last flare of the orb's magic, into a janitor in the Hong Kong branch of Stark Enterprises.