So I read this quote: "Does wisdom perhaps appear on the earth as a raven which is inspired by the smell of carrion?" of Nietzsche and I have no idea of what he is talking about here. Can anybody enlighten me?
See Twilight of the Idols, or How One Philosophizes with a Hammer (Götzen-Dämmerung, oder Wie man mit dem Hammer philosophiert, August-September 1888) : The Probelm of Socrates :
"The wisest men in every age have reached the same conclusion about life: it's no good ... What does this prove? What does it demonstrate? [...] these wisest men of all ages, let us start looking at them more closely! Perhaps they had become a bit unsteady on their feet? Perhaps they were late? doddering? decadent? Perhaps wisdom appears on earth as a raven, inspired by a little scent of carrion? [...] the great sages are types of decline [...] I recognized Socrates and Plato as symptoms of decay, as agents of Greek disintegration."
Wisdom is a product of decay, of decadence.
Nietzsche is talking about decadence, i.e., any approach to life, such as Christian morality, that leads to the decay rather than the flourishing of human beings. At the same time, he is commenting on the fact that over two millennia, so few people have recognized this: doing so requires genius. Consider this excerpt from Ecce Homo, Why I Am a Destiny:
"I know my lot. One day my name will be connected with the memory of something tremendous, – a crisis such as the earth has never seen, the deepest collision of conscience, a decision made against everything that has been believed, demanded, held sacred so far. I am not a human being, I am dynamite. [...] My lot would have it that I am the first decent human being, that I know myself as opposing the hypocrisy of millennia ... I was the first to discover the truth because I was the first to see – to smell – lies for what they are ... My genius is in my nostrils ... [...] ... I am a bearer of glad tidings as no one ever was before ... [...] ... all hope had disappeared until I came along. [EH Destiny 1] (bold emphasis added)
This renders the metaphor of the raven intelligible. As a raven smells decaying flesh, Nietzsche smells the decay caused by Christian morality. Nietzsche attributed his wisdom, or genius, at least in part, to his uncanny sense of smell: he was able to smell what so many others before him failed to smell.