You can buy it in the store (Siris) for 600,000
I think he means the old Infinity Blade. You can't get the old Infinity Blade yet, but it was hinted by Donald Mustard in the "Soul Hunter Preview" video that he could add in the original Infinity Blade.
Well, a new update has just released called 'Ausar Rising', and you can see the original Infintiy Blade in the trailer for it. Also, in the update among the secret items you can see the Infinity Blade's shape, so yep, you can get it now.... without a glitch.