Good vs Evil
There is a struggle between these two ideologies and this is physically represented by the battle between the Moroi and Strigoi. As a Damphir who is shadow-kissed, Rose is often unsure of which side she belongs to and this uncertainty is made obvious when she urges the Strigoi to drink her blood to turn her into a Strigoi instead of Eddie. Her shadow-kissed nature means that darkness always lingers within her, that forces her to act much like the Strigoi. However, her good side is retained by the love of Dimitri and Lissa.
Death
This is a key theme during Frostbite and is signified by Mason's death towards the end of the book. However, death is constantly around Rose in all forms, especially in the form of the Strigoi. She is constantly reminded of death by the fact that Strigoi must be killed. Indeed, the use of Strigoi is a metaphor for the idea that death is a constant presence and is a part of life. Rose too understands she must die one day but that she must die in battle and not by old age. Her easy acceptance of death is a reiteration of the fact that death is an inevitable process and is a part of life.
Duty
There is a heavy emphasis on this theme throughout the novel. Having been taught that the 'Moroi always come first' since an early age, Rose has a duty-bound complex towards all Moroi. Indeed, she resents certain Moroi such as Rafe and Queen Tatiana but nonetheless she protects them because the idea of duty is instilled within her.
Corruption of the Innocence
Lissa is a physical representation of innocence, with her loving, kind and caring personality. However, her innocence is tainted by the effects of Spirit. The feelings of darkness that linger within her and make her feel hostility towards people and act violently towards them is a constant problem that is explored in the novel. Her inability to stop such strong feelings of hate and anger are indicative of the fact that she is losing her innocence and her soul is being corrupted.
Madness/Insanity
Both Lissa and Adrian are physical manifestations of madness, a side-effect of Spirit. Lissa's sudden outbursts and Adrian's confusing ramblings suggest that both characters are losing their grip on humanity. Adrian's use of drugs and alcohol to numb the ever-present madness he feels is reflective of the fact that he is more towards the brink of madness than Lissa is.
