The Great Owl is an unplayable unit controlled by IDS. It drops bombs which devastate all units within three spaces. It appears in Chapter 22. It cannot be hurt by any anti air unit.
In Chapter 22, it bombs the center of the map beyond recognition. In Chapter 23, it starts directly bombing your forces, and does so for about 3 days (game time) but then retreats due to Isabella agreeing to go with Caulder. In Chapter 24, you must fight Penny and the IDS army on top of The Great Owl. The fight damages the fuselage of The Great Owl, causing it to crash.