We're leaving these somewhat mysterious for those who want to have that experience, but if you want to know what they all do, you can hop on over to the Release Notes
However, there are plenty of cards in Khans of Tarkir that are currently being overlooked by Commander players
These will be easy-to-complete tasks like Cast 30 White or Black spells or Play 25 lands
Paying a mere 3 mana to refill your hand, shuffle combo pieces back into your library, and deny your opponent's graveyard synergies all in one is just gas
Eloise, Nephalia Sleuth is a flavorful and mechanically interesting option for an alternative commander, while cards like Empty the Laboratory capture the polymorph dream, and Shadow Kin is just cool
You warp this in, play another land, and you suddenly have 8 power on board