As part of the Unified Community Platform project, this wiki and 38 others will be migrated to the new platform in the next few weeks. Minimal changes are expected as part of this migration. Read more here.
Each player chooses their favorite block and builds a Block Constructed deck. The twist is that each player's favorite block may be different! That means the best decks from Mirrodin block will do battle against the likes of the decks from Onslaught block. Or you can see how the dual lands of Ravnica block would fare against the denizens of the Masques block. Players build decks according to the Block Constructed rules from each of their blocks (including their Banned Lists, if any) and play following the normal Block Constructed rules.