Willow begins as a shy, sweet, bookish girl who befriends Buffy and does what she can to help her fight evil. As the show progressed, though, Willow evolved into a powerful witch with powers in her own right (even crossing over and becoming evil at one point). This character development lent both complexity and a level or reality to the show, since the character did not remain static.

A vengeance demon who eventually loses her powers and must adjust to life as a mortal again, Anya provided a great deal of humor and sweetness to the show. Because she didn't understand sarcasm or the need to be polite, she was often embarrassingly straightforward and honest, which created many opportunities for clever writing and laugh-inducing situations.

Most often providing the comic relief on the show, Xander's one-liners and hapless adventures (e.g., getting possessed by a hyena spirit, almost getting eaten by a giant bug, almost getting the life sucked out of him by an Incan mummy, etc.) lent a necessary levity to the show to offset some of the darker humor.

It is the creator of evils and the most powerful and is way cooler than some of the other characters on the list

The school librarian and Buffy's Watcher, Giles has a complicated past that is gradually revealed over the course of the show. This complexity of character was deftly handled by the writers and by Anthony Head, making Giles one of the most beloved and worthwhile characters on television.

The oldest and most powerful vampire to hit the buffy screen as well as the first

Cordelia wishes that Buffy had never come to Sunnydale, and an alternate universe is created in which both Xander and Willow had been turned into vampires. Vampire Willow is the exact opposite of sweet, shy Willow, meaning she is cruel and aggressive. The juxtaposition is both interesting and funny. When she accidentally gets transported from the alternate universe into the "regular" one, watching her try to adjust to a world not ruled by vampires is one of the most well-written and humorous character developments on the show.

She is the sister of the slayer and is a very important character to be included on the list