Who is Chigurh from No Country for Old Men and what is their importance?

Chigurh has eyes that are as blue as a piece of lapis and seem to glisten while at the same time are totally opaque. Chigurh has a reputation for being dangerous, and almost invincible. Those who know him refer to him as a psychopathic killer and the description is accurate. Chigurh is the kind of man who does not see that life has value.