"Considering that question is asked by a representative of the fey, the answer could be anything from 'singing

"Considering that question is asked by a representative of the fey, the answer could be anything from 'singing' to 'the love of pastries'! But let's think logically. The last part of the riddle can easily be ignored, because just about anything in the world can aid or ruin you depending on the circumstances. What's important is that the riddle clearly points to some quality or property of a living creature. Something that is born with us. Another point – it grows. I would say 'knowledge'. Each new day brings something new, so our knowledge of ourselves and the world keeps growing. For some, though, this process is ridiculously slow..."