On Corruption

We have witnessed that Corruption is a source of despicable evil, but how much do we really know of its origins? I know a Corrupted soldier could strike me down in a single blow, but why are they so powerful? Does the Corruption affect the muscles and sinews of the body? Or how hot the blood runs in the rage of combat? And what on earth causes that stench? Can they smell the reek of brimstone on each other? I can't imagine it makes for pleasant company. -Bao