Fisher King

According to Mirth, the agents of darkness spread throughout the world in many guises, while the agents of the light have only a few forms.  The Fisher King is one of the greatest figures of the light (although it is unclear why...he does not seem to actively do good, but merely be a symbol or carrier of the good), and the being that the heroes must protect.
 
The Fisher King wanders the world, appearing in different forms, although he/she is always lame.   He is hard to discover, Mirth says, for the same reason that it is harder to notice someone's good qualities rather than their bad qualities.  If the Umbra Sprite or the forces of darkness manage to kill him, they can use his blood in a ritual that will cause an age of evil to ensue.  They have done it before in the past, such as the end of the Roman Empire or during the World Wars.
 
The Umbra Sprite and his minions searched for him intently at first, by looking for lame homeless people.  Lazlo Grackleflint was clairvoyant, and could tell who he was if he touched him, so they often just had him go around touching the homeless.  Eventually Emil Grackleflint tried to put together a homeless mission to get better access to the homeless, but Kevin Matchstick and his companions set up ambushes and distracted them too much.  Lazlo was eventually turned into an invalid due to falling in his father's pit, and was no longer able to test the homeless by his touch.  They planned to hook him up to a radio station and use his powers to search the whole area, but once again Matchstick's group intervened.

However, Emil Grackleflint finally ran into the Fisher King directly in the form of a lame cat.  Emil stabbed him with his spur.  However, his death caused a burst of powerful energy which killed the nearby Lazlo and disfigured Emil. He then resurrected himself in a new form as a lame human and wandered away.  Emil apparently killed him the wrong way somehow, deviating from their prescribed ritual, and thus did not bring about the dark ages that they had intended.