The gryphons were not always monsters. That came later.
In the earliest days, they were our friends. They flew alongside pegasi. They shared the land with earth ponies. They studied beside unicorns. There was no fear between us. That came later too.
Time drew our people apart, but it was not time that made them monsters. They made that choice themselves; they chose their fate. And it was the greatest gryphon who sealed it.
He was born, many years ago, on a mountain far to the north...