As Thor seeks out and takes on the Serpent, the mysterious uber villain created for Fear Itself, the no-longer-old man acknowledges that he understands the prophecy. That Thor would kill the Serpent and then take nine paces before dying himself. That’s when he drops the bomb about who he truly is, albeit not with a name.
The Serpent is the uncle of Thor, and the rightful king of Asgard. His younger brother, Odin, took his throne and made himself King of the Gods, and binding his own brother away to insure his power. The prophecy was created in the act of binding the Serpent so that Odin would suffer if his brother were to die.
Well, Odin is a dick, but this is a bit much.