Special Skills have been added to Battle Mode. These are the same skills that you learn in the Story Mode, but it is not necessary to have unlocked them in the Story to be able to use them in Battle Mode.
Toggle the "Special Skills" switch in the lobby, then continue to the next screen to select your Disc (upper row) and Movement (lower row) skills. Disc skills can be used in battle mode using the Y button (on game controller) or E key (on keyboard). Movement skills can be used with the B button (on game controller) or right-click (on mouse).
Please enjoy duking it out with your friends using these special skills!