Unique Skills

Unique Skills (ユニークスキル) are «Extra Skills» in «Sword Art Online» that are assigned to only a single player per skill, while regular Extra Skills have at least 10 users per skill. Just like it is with Extra Skills, the prerequisites for receiving «Unique Skills» are unknown, but they are apparently given to players who fulfill a certain physical requirement. By the end of Sword Art Online, only two players were known to have Unique Skills: Heathcliff had «Holy Sword»; and Kirito had «Dual Blades».

Although Sword Skills were later implemented into ALfheim Online, certain suspicious conditional skills, including «Unique Skills», were removed from the system. It is rumored that about 10 skills were removed during verification, which is coincidentally the amount of «Unique Skills» said to have been created.

List of Unique Skills

 * «Dual Blades» - given to the strongest player.
 * «Holy Sword» - given to the player with the fastest reaction time.
 * «Darkness Blade» (暗黒剣)
 * «Battoujutsu» (抜刀術)
 * «Shurikenjutsu» (手裏剣術)
 * «Infinite Spear» (無限槍)

Trivia

 * The aforementioned «Unique Skills» apart from Dual Blades and Holy Sword were supposed to be unlocked after reaching the 90th floor.
 * Kayaba Akihiko had stated that Dual Blades was given to the player with the fastest reaction time. The chosen player was supposed to be the hero that would face him at the top of the 100th Floor.
 * Kayaba Akihiko also stated that there were only ten «Unique Skills» total, in contrast to the "unlimited" number of other skills.