Sirius' Bike and Mirror

"The two-way mirror given to Harry by Sirius Black and his flying motorbike will return. In fact, Rowling has mentioned in one of her FAQs that the two way mirror "will help more than you think." Rowling refused to comment whether Sirius himself might in some way reappear, but she has also said that there was a reason why he had to die."

Why would Sirius have to die? I can only think that perhaps it is because Harry needs to stand alone in the last fight. He has to feel that it is all or nothing and given really, no other choice.

I would love to know what that two-way mirror is going to be used for. Maybe the crew needs to go intot he forbidden forest and talk with each other? emember the mirror is now 'in pieces'. There is more than one or two. Could it be like walkie talkies or cell phones to muggles? hmm...

Got any ideas??

And about that bike, how wonderful would that be if Harry et crew traveled on it to the different places?