My idea was similar to your condition, except instead of the grim reaper, its basically all of Lennox's rage, saddness, regrets, and everything else he has held back over the years given life in his shadow and by the black blood.. This entity might actually become quite powerful because there has been a lot held back over the coarse of 11 long years. So its power is based more off his negative feeling then the positive ones and Lennox has felt almost nothing but negative feelings.