A divine spark is a mote of emotional energy, a fraction of the true deities heart. Nobody knows their true purpose. They are a remnant of Titan rituals to purge emotion and desire from the Empyrean noble class. Purified Empyreans were worshiped as gods by the Empyrean church. The church's view on the sparks is one of resentment. The titans purged these aspects for a reason, how the got into the hands of mortals is a mystery, but many Empyrean priests consider it one of Parun's worst pranks.
A divine spark is a tremendously powerful item. Free sparks readily bond with a mortals soul and consume it, merging with other souls previously incorporated. Those mortals with divine sparks, known as hero deities, become an amalgamation of all other mortal hosts. Some mortals with strong wills manage to overpower the personalities of previous holders, one such example is Yggritte. Others are consumed by the conflicting spirits within themselves such as Liadon or serve as an avatar for the will of an entire culture like the Daern.
Divine sparks grant a number of fantastic properties, not least of which is agelessness and control over the sparks emotional domain.