The Shadowmoor Expansion is made up of 301 cards based out by rarity in this order: 80 rare, 80 uncommon, 121 common and 20 basic lands.
This set plays on a level identical to the Lorwyn expansion, but due to an event called the 'Aurora', some of the creatures and characters are corrupt and twisted versions.
Shadowmoor is one of the few sets not released in the month of October by WOTC. It is also part of the Lorwyn block.
Note: The Shadowmoor set contains some reprinted cards from other expansions.