Many if not all dragons had a mate they were fated to meet one day, and if it took to long then they would see a red string that lead to their mate (red string theory)

In the 500 years that you were alive you had not once met your mate, so they day to saw the red string you didn't hesitate to follow but you. Thing is you didn't expect to see the dragons the humans called the destroyer, one who had killed hundreds of thousands of humans Dregon