It's a super robot that was developed by Tesla Leicht Institute, and is based off of the Gespenst Type S and Grungust Type-0. It's capable of adapting to many situations, since it has the WingGust mode for flight and its heavy tank Gustlander mode. It's equipped with special devices such as a voice recognition system, which is used for its attacks. Its long ranged abilities are rather weak since it was made for melee combat.
There are five variations of the head, and they are the Lion type for the second model, and Star type for the first and third models. The Hawk type was used for the prototype. The Dragon and Tiger types haven't been used yet, though they'll supposedly be used in future Grungust models.
The second unit is used by Bullet, and is a custom red color. It's similar in performance to Irm's Grungust.