Banefire appears as a scarlet and blue light becoming a white destructive fire which would kill the creatures imprisoned under Demonreach rather than allowing them to escape. It was put in place by The Original Merlin should there ever be a threat jeopardizing the prison.
In the seriesEdit
- Main article: Cold Days
In Cold Days, Demonreach shows Harry, through Bob's projection, a scarlet and blue light becoming a white destructive fire destroying everything. Bob explains that a directed burst of energy unraveling the containment spell Merlin would trigger the fire called the "failsafe".