Why Am I the Old One?

The prophecy left by the God of Time and Space points to a young man living in a remote village in Jianyue Kingdom. "Will he really become a god in charge of two divine weapons? Will he really lead another great era after the War of Gods and the Chaos of Gods?" What can he rely on? Strange abilities brought about by taking elixir? The spell industry of Jian Yue Kingdom? Elpop's steam technology and knights? Or the Gundam and satellite rail gun of Exnes?