To earn this challenge you simply have to complete the main campaign, working your way through the five planes. I don't have any real specific advice to give except you can make it easier on yourself by going to settings and changing the difficulty to 'Mage'. This will give you a leg up on your opponent and make advancing through each encounter much easier.
Minor spoiler here about the last fight with Garruk:
*** Spoiler - click to reveal ***This battle is actually a two-parter. You have to defeat him twice in a row and you can't back out or change decks in between the two fights.
I hope that helps you guys out. You may spend up to an hour on each plane, so this could take you 4-6 hours to get from start to finish depending on how quickly you defeat each opponent. If you get stuck on any specific area let me know and I can try to help you out. I've played a lot of magic in my time.