The Legend of Blah Blah Blah Blah

I think I was a little vague in my last post with reference to the major plot of the game and I admit that this reveals how terrible I am at stressing the importance of things.  Surely the plot of a story is the thing that should be explained in the most detail and not, as I have done, in one terrible run-on sentence?

So here it is in greater detail, and hopefully with fewer grammatical errors:

As I made it to the lowest sub-basement of Lysandre's Cafe Teleporter Maze-O-Madness, I happened upon Lysandre himself and a mysterious man I had seen only once before.  Lysandre was obviously holding the eight-foot-tall man captive (the electrified fence gave that away) and the captive launched-into a monologue describing the 3000-Year Legend:
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Three thousand years ago into the future, back when everything was in black-and-white and there was a lot of film-grain and text on the screen explaining what the actors are doing (fine, I'll stop), there was a man who loved his Floette.  His Floette went off to fight in a war between two nations.  Floette never came back.

The man was apparently so angry that he used science and magic, but mostly science, to resurrect his Floette with a machine he built, but to power his machine he killed scores of other Pokemon in the process.  As it were, all those strange stones around Geosenge City are gravestones of these pokemon, which is just creepy enough to be totally awesome.

After this, he was still really really angry, so he modified his resurrection machine and made it a doomsday weapon, which he used to kill a whole bunch of people and pokemon, ending the war.  A little bit of an overkill, but most definitely effective.

Then his Floette left him anyways.  It's times like these where I wish I knew the definition of irony...

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I am about 100% certain (you read that right) that the old giant in the prison cell was that man from 3000 years ago and if he isn't then he definitely thinks he is--because he all but admitted to it during his monologue.  I am very curious, however, how the legendary pokemon Yvetal relates to this.

Professor Sycamore told me earlier that there was a destructive pokemon called Yvetal linked to the 3000 Year Legend, but this pokemon was not mentioned even once...  Maybe the answer can be found in Geosenge City.