As my story is weaved heavily with Celt mythology, I use existing creatures not only from Celt mythology but other mythologies as well. For example I use a group of Talos, giant men of bronze, which derives from Greek mythology in the climax. Hey it's fantasy and there are very few rules...
I do not believe that using elves is a cliche. I have read several stories where the author has created so many races with different names, I find it confusing. I use fairies in my story, with one troll, but I also use creatures from Celt mythology that readers may not be familiar with but their...