Ghosts
The presence of the ghosts in this book draws further attention to Rose's shadow kissed nature. Previously, her only difference was her spirit bond with Lissa but now the fact that she can see ghosts foreshadows the shadow-kissed links in the next books. Also, it suggests that Rose shadow kissed nature is becoming stronger and her connection with the dead more concrete.
Stake
The stake represents both life and death. It is infused with all the elements of life; earth, fire, wind, water, and spirit. And yet its purpose is to kill. The juxtaposition highlights the battle between good and evil.
St Vladimirs
The school is secluded from all areas and is located in Montana, which is surprising because of its weather. Vampires/Strigoi cannot go out in sunlight and Moroi's become strongly depleted by it. The idea that the Strigoi are able to carry out these attacks in this temperate suggests that they are becoming a stronger and more united force in their fight against the Moroi.
The Cabin
The Cabin begins to hold a turning point in Rose and Dimitri's relationship. They have sex, which is clearly against the rules between student and instructor, and as they speak of finally being together, it is ironic because the cabin is hidden away from each other. Their relationship, though strengthened, is still considered taboo.