Who is Jace Wayland from City of Bones and what is their importance?

Nephil Shadowhunter, Jace Wayland, meets Clary at the Pandemonium Club. The fact that she is can see Jace through his glamours tells Jace that Clary is not a normal human being (mundanes). Jace introduces her to their way of life, during which time, he falls in love with her. Sadly, the pair learns that they might be brother and sister (they aren't). Jace is described as brash, bold, arrogant, and lethal.