Mercadian Masques contains 350 new cards for Magic: The Gathering. Each booster pack contains 15 cards including 1 rare, 3 uncommon, and 11 common cards.
Mercadian Masques was the first set after the broken Urza's block, and the developers were a bit gunshy. THat said MM was a much more balanced set. It was this set that last saw the appearance of Dark Ritual, a staple black common from the days of Alpha. Many cards from this set will continue to see play in the Extended format until the rotation that occurs when Ravinca becomes tournament legal in 2005 -- By MtG-Arghun from Sitkum, Oregon on March 13, 2005