J.K. Rowling has just given us another clue to Book 7. In a recent interview with Helena Bonham Carter, she let on that Rowling revealed to her that Bellatrix will be very important in the last book.
Bellatrix Lestrange had been mentioned in a couple of the middle books of the series, but she became important in Order of the Phoenix, when she broke out of Azkaban and participated in the Battle at the Ministry in the Department of Mysteries. We know that Neville especially has it out for her, since she was one of the Death Eaters who tortured his parents into madness. Will the two of them be part of the climactic battle in Book 7?
Bellatrix also considers herself one of Voldemort’s most loyal followers and might have had a lot of inside information into the Death Eaters and Voldemort’s use of horcruxes. Being a cousin of Sirius and Regulus Black’s, did she know anything about the locket?
And, what I consider to be most important, why did she torture the Longbottoms after Voldemort had already disappear? What did she believe she had to gain?

September 16, 2007 at 4:31 pm
In answer to “why did she tourture the longbottoms after voldemort disappeared?”
Bellatrix must have believed the Order Of The Pheonix knew something about Voldemorts disappearance so she and some others (Barty Crouh jr, Rodolphus and Rabastan Lestrange) set out to interrogate members for information. It was probably just coincidence that they attacked the Longbottoms first.