Spirit Light is a pickup found in Ori and the Blind Forest and Ori and the Will of the Wisps.
Ori and the Blind Forest
Spirit light is obtained by defeating enemies and picking up Spirit Light Containers. Once the player has collected enough, they will earn an Ability Point.
Ori and the Will of the Wisps
Spirit light is obtained by defeating enemies, picking up Spirit Light Containers, completing side quests, and completing Spirit Trials. Any Spirit Light the player has collected can be used to purchase goods from various friendly creatures.