Who is Molly Malone from On a Pale Horse and what is their importance?

Molly Malone is the ghost of an Irish fishmonger who roams the streets of Zane's home city hawking cockles and mussels. She was summoned through magic to the city of Kilvarough as a mascot, but she is not very popular since she has a special talent. Anyone who Molly can see and interact with is near death, so if someone is seen by Molly, that person knows he or she is going to die. Zane saves Molly from a mugger before his death, and she later leads him and Luna to the carnival of ghosts. Molly also acts as Zane's companion on his tour through Hell, and she is able to reveal to him that souls are not reformed in Hell. They are merely tortured and kept in Hell. No soul has ever left.