Twelve is a mutant, part of the G-Project, a biological warfare operation run by a mysterious organization under the control of Gill. Twelve is a milky-white being with no form of skin or tissue. He has very thin eyes resting on his oddly-shaped head. He wears no form of clothing and is humanoid in body shape but, as his story says, can change his physical shape as the situation demands as well as mimic another person.
With Necro being his prototype, Twelve is genetically engineered to regenerate, form other shapes (usually weapons) out of his body, copy a person's appearance and skill, and is meant to be incapable of being damaged. The "G-Project", the secret project that resulted in Twelve's birth, was executed by Dr. Kure, and overseen by Gill's brother, Urien. Twelve is ordered to retrieve Necro and Effie after the latter freed and helped Necro escape from Gill's organization. Twelve is also being mass-produced by the organization to create an army of Twelve-like creatures. Twelve considers Urien to be his father because of his involvement with his creation.
Twelve has a very unusual fighting style. He is the only character with an airdash, which can alter the arcs of his jumps, he can also "crawl" on the floor, evading many ranged attacks like the Hadouken without having to block or parry. Twelve can also render himself invisible for a short time using his personal action. Twelve also cannot utilize the Red Parry unless you pick the Red color with the Heavy Punch button on the character select screen. Twelve appears in Street Fighter III: 3rd Strike and otherwise has few cameo appearances or related merchandise, which is unusual for a Street Fighter character. He does appear in SNK vs. Capcom: Card Fighters Clash.
When you perform Twelve's personal action (+), he turns invisible, and remains this way for a limited period of time, or until he is hit, he blocks an attack, or he performs a hold or Super Art. Note that he won't turn visible after parrying attacks, using (or getting stopped by) the Grap Defense, though. If you do an EX special move, the EX 'flash' will still appear on-screen. If you use the X.C.O.P.Y. in a Twelve vs. Twelve match, you won't be able to turn invisible, even though you're still Twelve. Once invisible, you can press + to taunt and reappear.
|__Wall Bounce||(Near wall during Air Dash)|
|I X.N.D.L.||+||(x2 meter)|
|II X.F.L.A.T.||+||(x1 meter)|
|III X.C.O.P.Y.||+||(x1 meter)|