Siobhan is the leader of the Irish coven, which includes her mate Liam (a complete non-entity) and "Little Maggie" a
human vampire lie detector. Carlisle believes she has the ability to make events turn out how she wants, but this ability is questionable, as she doesn't believe in it, and one would think she probably ought to know. Some fans believe that the ending of Breaking Dawn, in which she gets what she had been visualising, constitutes proof that Carlisle is correct, but actually the direct intervention of god Smeyer on Bella-sue's behalf is a more likely explanation. Siobhan is described as quite large, and graceful.