As villains go, Two-Face is the personification of the term "alter-ego." Once the highly respected District Attorney Harvey Dent, Two-Face has since taken his place as one of the most nefarious split personality cases since Dr. Hyde.
Two-Face first surfaced in Detective Comics #66, his villainous transformation the result of a tragic tussle with the evil mob boss, Maroni. During the altercation, acid manages to destroy the entire left side of Dent's body. In an ironic turn, the grotesque disintegration of tissue and the scarring it leaves behind trigger Dent's afore-latent split personality disorder.
As split personalities are wont to do, Harvey's alterego went stark raving mad, terrorizing all the citizens he once vowed to serve and protect. Though remnants of the old Harvey still surface every now and again to reacquaint the character with his humanity, Two-Face clearly possessed the upper hand in dominating the tortured soul's actions.
Two-Face, like all the legendary villains of our time, had a fabulously absurd arsenal of eccentricities. He became obsessed with the number two. He took to adorning himself in ornate colors like lime green, grapish purple and tangerine. And he allowed all his actions to be governed by a damaged silver dollar. One side of the coin was smooth and unmarked, while the other was distorted and defiled. When a flip of the coin resulted in the appearance of the smooth surface, the former Harvey shone through and gained ground in the fight for sanity. More often than not, though, the scarred side surfaced and Two-Face prevailed.
Though he has appeared to die many times, Two-Face has managed to match his nocturnal nemesis, Batman, blow for blow for decades. He continues to wreak double-minded havoc even today.