Answer:
I fly forever Rest never.
I stink up your breath and fights evil vampires
You use a knife to slice my head and weep beside me when I am dead.
What tastes better than it smells?
I am the type of room you cannot enter or leave. Raise from the ground below I could be poisonous or a delicious treat.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.