Ten years before the events in Kingdom Hearts: Birth by Sleep , the universe is still how one remembers it. Maleficent from the Disney-movie Sleeping Beauty is only a threat to Princess Aurora, Peter Pan is still fighting Captain Hook and Experiment 626 has yet to escape the clutches of the Universal Police - all enclosed in their own little worlds with no contact to the outside. In-between on the Isle of Departure are Terra, Ventus and Aqua - a trio of friends and Keyblade wielders who want to become masters. While Terra and Aqua are already ready to take the exam of mastery, Ventus still has a long way ahead of himself. During the exam however it turns out that even Terra isn't ready yet, unable to control the darkness within his heart. At the same time the universe is suddenly threatened by the Unversed - creatures of pure darkness who appeared on the different worlds and wreck havoc under the Disney-characters. To make things worse, Master Xehanort disappears. So Terra and Aqua are tasked with destroying the Unversed and finding the missing Master. Unknown to Terra however, Aqua has a secret mission: watching Terra in order to find out if he can control the darkness within him. Ventus on the other hand is goaded into following Terra by a mysterious other character...and so the adventure begins.
In its core Kingdom Hearts: Birth by Sleep follows the same principles as the other iterations of the series. The game mixes gameplay-elements from the Final Fantasy series with characters and locations from Disney-properties like Mickey Mouse. To that end the player visits the Dwarf Woodland, the Snowfield, the Moogle's Village, the Frozen Falls, the Castle, the Old Town, and the Temple - all simply called worlds - which allows the character to battle enemies, collect items and level up.
The command deck contains up to eight techniques, abilities and spells - all simply called commands - which allows the character e.g. to heal himself or throw his keyblade at the enemy. After the current command is used, the deck automatically switches to the next one while the previous one regenerates until it can be used again. So instead of mana, the only resource is time. Each of the commands will automatically level up just by using it up to five times depending on the command increasing the damage it deals and unlocking additional command styles and finishing commands.
New Commands can either be bought at shops, created through crafting or by playing some of the five included mini-games. Crafting involves merging two higher level commands using a crystal into a new command. One of the mini-games is simply called Command Board - a Monopoly-knock-off in which the players place commands on a bought field instead of buying streets and planting hotels.
The game features a multiplayer-mode for up to six players via ad-hoc-wifi allowing them to play "Command Board", fight each other in death match, play the mini-game "Rumble Racing" - a Mario Kart-clone - or fight side by side in Survival Modes against hordes and hordes of enemies including boss fights. Multiplayer even features additional commands not available in the normal game.