Those flashback cards and reanimation are just the start, exile cards from your graveyard, shuffle them back in your library, or feed them back into your hand, the ways are numerous
Have an army of Demons ready before attacking, so you can start taking big chunks out of your opponents' life as they are forced to sacrifice half of their permanents
Magic: The Gatherings upcoming crossover with television series Doctor Who will feature legendary cards based on every single Doctor
It features a full cycle of on-color indestructible lands as well as bounce lands (allowing you to replay lands after remaining lands are destroyed), as well as a ton of mana rocks that will survive past your Armageddon effects
So, you can have one copy of Thalia, Guardian of Thraben on the battlefield, but you cannot have two copies of Thalia, Guardian of Thraben