But would it still work now that some of them had mated with humans?
When Ferdinand and his fellow primordial dragons were all in hibernation, humanity had the chance to wipe out all the long-lived races since the young ones grew too complacent and weak over the years.
However, now that Ferdinand and the others had been awakened from their slumber, humanity had no chance to win another Great War.
If he was allowed to use his real body, Ferdinand all alone could raze one continent to another in a single day. Especially now that humans only had a few mages left compared to the past.
The only protection humans had now that could likely hurt the long-lived races was the Pope and the Great Temple since they had access to resources that could kill the long-lived races.
But of course, such things would not be able to kill Ferdinand and the primordials. Only the young ones.