Fire of Purification

This is the root of the so called blue fire spells developed to combat demons and the undead. In general these spells mimic normal fire spells, in terms of damage, range and cost to cast, but with a few key differences. Blue fire spells only damage undead or demonic entities they will not inflict damage on creatures that are not supernatural. Blue fire spells will not set fire to any objects unless they are supernatural in nature.

Effect

These spells all cause direct damage to undead or demonic creatures and have zero effect on living beings, even of the magically enhanced variety. This means a warrior could be being swarmed by a pack of zombies and caught in the middle of a ball of blue fire without any ill-effect while the zombies burn to a crisp.

Manifestation

Blue fire spells look like flames , but appear to be entirely bright blue in color.

Source

Well typically being used as a cast spell by both clerics and magic users, blue fire spells are also launched by purpose made artifacts such as wands, rings and amulets.

Discovery

These spells were originally developed by the Grave Wardens, but soon spread to other groups as well as magic users concerned with defeating undead and demonic entities.