Who is Jane from Eclipse and what is their importance?

Jane is a member of the Volturi. She has the power to cause vampires great pain without touching them. For some unknown reason Bella is immune to this power. Jane dislikes Bella and wants to kill her because she knows about the vampires, but the Volturi has decided that if the Cullens turn Bella into a vampire then there is no reason to kill her. Despite this, Jane remains a danger to Jane and will more than likely play a significant role in the next book in this series.