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A Barrier Master is a rather small Heartless that wears long robes that cover its feet. These robes are predominantly indigo and navy blue, with a light green collar and a number of white designs decorating them. It also wears a tall, cylindrical, indigo and white hat and what seem to be light green gloves. The only part of the Heartless not covered by clothing is its face, which is spherical, navy blue, and sports yellow, glowing eyes. All Barrier Masters hold a dark blue book that they use as a shield.
The Barrier Master's name clearly references the magical shields it creates, and its skill in doing so.
The Barrier Master uses its large book as a shield, similar to the defensive methods used by the large-bodied Heartless. It can only be attacked when separated from the book, which is also used as a weapon with magical powers, the Heartless stunned upon this separation. However, it will soon "wake up" and will start moving towards its book. If it successfully reaches the book, it will once again use it as a shield. The book can be knocked away by attacking it, though.
If it is away from its book for a long time, the Barrier Master can summon a new book, which also has to be separated from it. As this Heartless occasionally appears with another, stronger Heartless, the stronger Heartless cannot be hit, as the Barrier Master will protect it with a spell. The only way to remove this spell's effect is to defeat the Barrier Master.