Shards od Alara is set 1 of 3 in the Alara block and contains 249 Cards (15 mythic, 53 rare, 60 uncommon, 101 common, 20 basic lands)
Alara was whole once. But that was millennia ago. Where once there was a plane, now there are five: the Shards.
The plane of Alara was a world rich with mana, a world in balance...until the Sundering. In a cataclysm of unimaginable proportions, Alara was rent asunder into five separate worlds, each a refraction of the others.
The cause of this cataclysm has been lost to time. Some ancient lore of the Shards suggest a being of godlike power forcibly split Alara to seize its mana for himself. Some believe it was caused by the titanic battle for the fate of Alara, waged by the archangel Asha and the demon Malfegor. But for most, only the dimmest cultural memories remain of a richer world that existed before their own.
Whatever the cause of the splitting, one thing is clear: The Shards have become very different places in the time since the Sundering. Each plane was all but severed from two of the five colors of mana. The Shard of Bant, for example, lost almost all its black and red mana, maintaining only white, blue, and green.
This mana imbalance caused the Shards to evolve in wildly distinct directions over the course of thousands of years. Now only hints of a common ancestor plane remain on the five worlds, and their environments and denizens could hardly differ more.
* Starting with Shards of Alara, every booster pack will have one rare (roughly one in eight packs replaced by a mythic rare), three uncommons, ten commons, and one basic land. This new rarity distribution will be applied to every core set and expansion (large and small) moving forward.
* Mythic rares have a new expansion symbol color (copper red)
* Mythic rares are expected to mean cards like Planeswalkers, most legends, and epic-feeling creatures and spells. They will not just be a list of each set's most powerful tournament-level cards.
* Mythic rares have premium (foil) versions as well
* The number of combined premium rares and premium mythic rares you will get starting with Shards of Alara is higher than the number of premium rares you currently get.