The necklace represents, the firebird prototype that allows anyone to travel to any dimension they want. In the book, Marguerite convinces Theo to go with him on find her dad's murderer. Theo gives her the prototype, and puts it around her neck. The firebird was named after Theo's 1981 Pontiac Firebird, that he rebuilt himself.
1970 PONTIAC FIREBIRD This stunning machine is the creation of award winning custom shop All Speed Customs. They were commissioned by owner Tom Cronkright to custom his 1970 Pontiac Firebird into his dream car. His vision was to tastefully integrate modern styling and technology into the classic 1970 Pontiac Formula Firebird body. He requested luxuries and appointments found in late model sports cars.