Fae nature: different, not just powerful
The most important craft decision in fae fiction is how to make the fae genuinely Other rather than merely powerful: beings whose difference from humans is structural rather than just a matter of degree. Fae otherness can operate along several axes: temporal (the fae who has lived for millennia and experiences human life as briefly as a mayfly), aesthetic (the fae for whom beauty is an absolute value that governs all decisions), moral (the fae whose relationship to human concepts of good and evil is genuinely foreign rather than simply different), and cognitive (the fae who cannot lie directly, whose relationship to truth is therefore structured completely differently from a human's). Choosing which specific axis or axes of otherness to develop, and being consistent about their implications, produces fae who feel genuinely alien rather than human in costume.