It is a time of darkness. You'd never have guessed that from the title eh. The great Ozrah choppy sword thingy has been stolen. Battle against the forces of Hellgilliantailforthium to retrieve it. On your way meet many extremely huge and very nicely rendered beast things.
Think of this as "Darksiders II with all the bits already completed before they released the DLC plus free Darksiders 1". I think it's a bit of a bargain - if you're one of the 12 people left in the country who hasn't played the first Darksiders.