Soulfire

Soulfire is the ability to use the soul as a power-boost in magic, affiliated with heaven. It is the antithesis to Hellfire. Soulfire uses part of the human soul, which regenerates over time and through acts which are "good for the soul", but will kill the user if it is completely drained.

In the series
At the end of Small Favor, Soulfire was given to Harry Dresden by the archangel Uriel, after he had lost Hellfire when the Shadow of Lasciel (Lash) was erased from his subconscious mind at the end of White Night. Soulfire has manifested as a silvery ghost of Harry's force spell, and a blue-white supercharged version of his fire blast. Harry was told by Bob about it's use of the human soul.