Oh, shut up and help me remodel the Barrier (status) page!
The Barrier status is set by the Lunar Curtain item, granting immunity to physical attacks, making all physical attacks automatically miss. The Barrier status can be Dispelled, and can also be removed by Black Hole.
The Barrier status returns as a status effect in the sequel of Final Fantasy IV, and it functions the same way as its predecessor.
Lunar Curtain returns in the sequel, and it functions the same way as it did in the prequel.