Light is a type of supernatural phenomenon that is wielded by priests and heroes to heal and combat Evil. Angels have some relation to the ability to wield Light. It is known to be anathema to demons, and is able to be manipulated in a way that is similar to sorcery. The precise mechanics of its usage by priests are unknown, but it is believed to be used through prayer. Heroes are able to manipulate Light in a similar way as using a Name.
Light has two main usages, combat focused and healing focused. Tariq has said that strength in of one of these types typically precludes strength in another. However, he is an exception to this rule as he has been called the best healer alive and is also an extremely capable combatant while wielding Light.
Light when used in combat is typically used to empower and shield heroes. It allows for them to perform superhuman feats such as cracking stone with their bare hands. Lanterns, a type of warrior priest found in Levant, also use Light in combat. They appear to use it as a type of beam weapon, as shown in the Prince's Graveyard.
Light when used to heal has been noted to be very effective. It is quicker and easier than similar healing done with magic. Light has even managed to resurrect people, although it was done by Tariq, a very skilled healer, while using an aspect.