Legend of the Dragon Slayer: The Origin Story of Dragonwatch

Legend of the Dragon Slayer is a short prequel to the Dragonwatch series. It can safely be read at any time. While it does provide some background to a minor character, it is not critical for understanding the series. The original "dragon slayer" was the son of a cobbler. He was willing to go out and fight enemies that nobody else was willing to battle. Through this willingness to fight he eventually came to marry the princess and inherit the kingdom. 

As with most hero stories, the tales of his bravery were greatly exaggerated over time. He later admits that he himself had started the exaggeration. While his original stories had him luckily defeating the monsters, he actually stumbled across them already defeated, and just ensured they were gone before extracting a talisman. 

As a ruler, he was summoned to fight a pillager that was called dragon. This would be actual combat, so he could not rely on luck. However, he could use the talismen that he procured and would defeat him in a David vs. Goliath contest. This probably contributed to his reputation as a "dragon slayer". It was only later (in a time not covered by the book) that he would actually fight dragons.

The takeaway seems to be that nothing ventured, nothing gained. There were plenty of other legitimate warriors. They could have gone out and gathered the rewards he did. However, none of them were willing to go. Being willing lead him to the initial rewards. However, that was not enough. He would have failed the final battle if he had not used the experience from what he previously accomplished.