You create an immobile sphere or hemisphere of force around your square or squares. The force barrier functions as a wall of force in all other ways. Activating this ability is a standard action, and the barrier lasts until the beginning of your next turn. Each round, just before the barrier would disappear, you can extend its duration by accepting 1 point of burn. If an attack manages to destroy the force barrier, you immediately take 1 point of burn.
