The Goddess took an ember from Alanna's campfire in the beginning of "In the Hand of the Goddess" and asked Alanna to accept it. When Alanna to it, the ember was cold and seemed to burn inside a crystal shell. The shell had a loop in it from which Alanna could hang a chain later should she desire.
Later, she put it on a gold necklace and wore it around her neck. She discovered that if she touched it, when someone was using magic or had put magic into an object, she would be able to see the color of their magic even if it wasn't visible to the naked eye. She used this on several occasions while fighting Roger of Conté.
She told her brother Thom about the ember-stone while she visited him in the City of the Gods. He cast a spell for it to reveal it's secrets, but it withheld his attempts, making him certain that it came from the Gods. This was the first time she told anyone about the ember-stone and how she had gotten it.
The ember-stone sometimes warns her of coming dangers.