The Stone of Darkness: The Dragonslayer Series, Book Three of Four

In book three of the Dragonslayer series, Astrid accepts her duty and follows the winter route - until she's bitten by a dragon.

Everyone knows dragon bites are poisonous and deadly, so she reluctantly accepts her impending death.

In a twist of fate, she survives.

Desperate for an explanation, Astrid believes she has somehow been protected by the black stone she keeps with her at all times, a stone that emerged from the sole of her foot a year ago.