Athos: The Return
If the urn increased our power then we should be able to release its energy just like Nox. So I practiced honing in on it and eventually, it didn’t take very long, I was able to release what little of the power I had. A blue spark jumped across my hands and with it came a surge of energy. It was like the life force of several creatures flowing through me.
-Simon Bloom, The Labyrinth
The thick blue energy known as Spirit Fuel seems to have been created by Nox through thousands of years of perfecting it. Spirit Fuel seems to be created by slowly draining the life force of a creature, and as more life force is drained, the more energy is created. While it is unknown exactly what this energy is used for or designed for, The Party has seen it in action on several occasions.
Although at first it seemed that Nox had created this energy, the demigods have learned that he did not. The energy exists as a counterbalance to Athos’ power, and seems to have been created when he was. Although each Urn seems to have a unique strand of Spirit Fuel, they can all be clearly recognized as the same type of energy.