Quote Originally Posted by mighty
Why you need an already used monster in your story?
Why don't you create a fresh one for your story?
A great many of the creatures in J.K.' stories come from old mythology that she revamped in order to fit into her story: centaurs, the basilisk, even veelas. She did make up several of her own monsters too, but the great majority of them came from research into stories that already existed.

So yes, it would be possible to create my own moster, but basing one on an already-existing creature would be...brownie points.