Henry realized that it was going to be a pity for him to be killing the dragons. Additionally, he was quite curious about the method that the dragons had utilized in order to be able to turn the humans on this continent into dragons.
After inquiring about it, there was no dragon that was willing to inform him about it. In the end, he was forced to use his strength to tame the dragons. And with that, him managed to get what he wanted after a few questions.
He came to realize that there was a method that the dragons had utilized. There was an item that they had utilized in order to be able to transform the humans into dragons.
They actually did not know the name of the item, and neither did they know the full uses of that item. In any case, they understood that that item could be utilized in order to be able to transform the race of a person.