TBN

A universe where "magic" is a biological chemical produced by certain species. Humans, alone on a world similar to Earth, harvest this substance from large birds, whose migratory paths require travel from planet to planet. What once was their hunting ground is now their graveyard, though extremely difficult to track, and even harder to kill, humans kill as many as they can. This chemical is refined into a fine oil, that when injected through the eye and mixed with the cerebrospinal fluid allows the user the practice an art called "magic" by the commoners.