Shadow Moves are enhanced special moves present in most Killer Instinct games. The way they are performed changes from game to game, but they are always identifiable as powerful attacks that leave the character with a shadowy trail.
Shadow Moves are a form of Post-Combo Breakers, only available with the flashing white line present on the player's lifebar. Each character has only one or two Shadow Moves at their disposal, usually requiring a Fierce Hold/Release input of a special move.
Some Shadow Moves can be used as powerful enders for combos. Using an Ultra Combo with the flashing white line will automatically cause the Shadow Move version, regardless of input.
On the SNES port, Shadow Moves retain their qualities but without the shadowy trail effect.
Shadow Moves return in Killer Instinct 2 and its port, Killer Instinct Gold. They function largely the same, although this time they are a form of Super Move (normally using 3 blocks of the Super Meter) distinguished by the signature shadow trail. Not every character has a Shadow Move at their disposal.
In the Killer Instinct reboot, every character on the roster has access to at least three Shadow Moves. During the first two Seasons they retained the inky black trail of previous games, but in Season 3 updates the trail was changed to purple to better reflect the game's color scheme of green and purple.
Shadow Moves are performed with the input of a character's Special Move, but with two buttons of different strengths (ex. LP+MP) instead of one. This uses one bar of the Shadow Meter. They often have improved properties, such as enhanced damage or projectile invincibility, and hit anywhere from three to ten times consecutively (most have five hits). Shadow Moves can also operate as openers, linkers, or enders. Some Shadow Moves are entirely defensive in nature, such as Omen's Shadow Form or Arbiter's Energy Shield.
Shadow Linkers are special in that they require three button presses to Combo Break, each resulting in a yellow flash and the announcer counting to three. Button strength does not matter, only timing. The attacker may cancel their own Shadow Linker with a Counter Breaker to retaliate against this.
Shadow Counters are a new technique that every character can use to counter an attack for the cost of one Shadow Meter bar, retaliating with a set Shadow Move.