Mesa

Mesa is the Light whose mind was meant to be merged with the mind of the Juvo Nexus. When Igz interrupted the process. His mind was lost in the Dren's empty space until Jack found it. The being living in the empty space seriously damaged the interconnecting parts of his mind when they tried to communicate. They did not know they were causing damage so continued trying over the ten thousand years he was lost. When Jack found him, he sensed almost nothing but fear in his mind. Fortunately that was due to the damaged areas and did not have any lasting effects on Mesa.