Gratan is designed and built from scratch by skilled mechanic Hanson. It is a small multi-purpose vehicle: it has wheels for ground movement, but may also fly using a hot-air balloon and propellers, and even travel underwater. Configuration can be switched by the pilot using a piano keyboard in the cockpit. Gratan, whose original meaning is "Grandis' tank", is the common name for the vehicle, while Grandis prefers to call it "Katherine."
After being damaged and repaired countless times during the series, Gratan is eventually crushed by the igniter of Red Noah's Light of Babel, a sacrifice needed to avoid destruction of a defenseless Excelion.