Charles Xavier is no more. Not long ago, it emerged from within Xavier's darkest subconcious and most hidden fears to reveal itself upon the world. For days now, Onslaught has feasted on a world filled with terror. But something yet denies Professor X the honeyed taste of victory. They are the X-Men, Avengers, and the Fantastic Four, the greatest heroes this world has to offer. Soon, amid a swan song sweet with justice, they shall split the monster's belly and leave Onslaught choking on the very darkness that seethes within his soul. But at what cost?