Behind the light awaits the shadows

There is a murder on the loose in Mirkwood, someone is killing elves and this creature is both cunning and sly. Thranduil and his men are trying to find the culprit while he is trying to protect his loved ones. What would it take to turn an elf towards evil and darkness, how would it change him? And how would you stop such a creature? Sad story, a little disturbing, you are warned.