Dimensional Cape (ディメンジョンマント Dimenjon Manto, Dimension Mantle) is Meta Knight's down special move. It seems to have debuted in the first trailer, when Meta Knight avoided Pit's Palutena Arrow. It is apparently different or toned down from the trailer appearance, much like the Wario Waft. When describing down special moves, Dojo!! states that "Many of these do unusual things, like reflect enemy attacks," suggesting that the Dimensional Cape has such a property, especially from what the trailer showed. This is not true as no hitbox of the move can reflect. The slash after the Dimensional Cape does around 14% of damage, and some knockback. Many players disregard the cape, but it is very useful for surprising opponents, making recovery less predictable and for edgeguarding.
It actually makes Meta Knight teleport for a short distance in any direction; When the player uses the technique, moving the control stick in any direction the player wishes to move and holding the special button causes Meta Knight to reappear and slash with little effort. However, Meta Knight, while using this move, is invisible, but not invincible, and can be hit by any attack during the teleport, a fact CPUs often exploit (which is exacerbated by the fact that they often exhibit frame-perfect reactions).
Meta Knight will slash in the opposite direction in which he moved while using the attack (moved left, he will slash to his right side - moved right, will slash to his left side). If the player performs the move downward while on the ground, Meta Knight will stay in the same spot he was in, and will slash in the opposite direction he was facing before using the attack. This downward directional can be used as a sort counter move if timed correctly.
Meta Knight can use this move as a recovery move, but afterwards, he will enter helpless state. This move is commonly used as edgeguarding. This is an extremely "flashy" move, and is often used for showing off.
 Ledge techniques
The Dimensional Cape can be used for edgeguarding in a number of ways. A few of these are listed here:
Dashing Dimensional edgehog: Dash toward the edge and use the Dimensional Cape. If the player is at the right distance, Meta Knight will fall over the edge and grab it. The player has a very small DI influence, so they can lean toward the edge slightly if they are about to SD. Doing this technique at the wrong distance will result in either an SD or not reaching the edge. It is used to reach the edge quicker for edgehogging.
Dimensional edgestall: By pressing down on the control stick/d-pad and the special move button, Meta Knight will perform the Dimensional Cape while falling slightly off the edge. Quickly tap the control stick/d-pad upward, then return it to its neutral position. If done correctly, Meta Knight will reappear right on the edge, and will grab it. This can be used to create an endless edgestall. The player can also use the cape without tapping the stick downward or moving it after the player initates the move, resulting in disappearing and reappearing in place. If done wrongly however, this will usually result in an SD.
Dimensional edgeguard punish: By performing the first part of the first Dimensional Edgestall method above, but by keeping hold of the special move button and keeping the control stick/d-pad pointed upwards, Meta Knight will reappear right next to the edge and perform the slash, punishing edgeguarders. the player can move slightly to the left and right by holding the stick/pad diagonally upward.
Its possible to do an Infinite Dimensional Cape where Meta Knight can be invisible for periods of time. This technique is banned from tournaments due to its potential to stall matches. This technique is performed by holding down on the analog stick and very quickly using the u-smash repeatedly after the activation of the move.
 Description from the Instruction Booklet
Vanish with a flourish of his cape. If you hold down the A Button, Meta Knight will attack upon reappearing.
This move is likely based on Meta Knight's ability to teleport using his cape in the Kirby games. Usually, after he is defeated in the games, his mask falls off, and after realising this, he wraps himself in his cape and jumps, disappearing. It is not too much of a stretch to suggest Meta Knight could use this technique as a sneak attack. However, Meta Knight prides on honorable fighting.
He is also seen doing this move in Kirby Super Star to destroy the platform he is standing on and make a dramatic entrance.