Aerial Fortress Gool is an aerial machine that serves as both a vehicle of transport and as a weapon in the Mazinkaiser series. Unlike its counterparts that are known for being controlled by Count Brocken, the Gool was controlled by Baron Ashura.
In the OVA series, Gool was used by Ashura in a plan to capture Mazinkaiser. After releasing Mechanical Beasts onto Tokyo and the Photon Power Lab sent their robots, Baron Ashura proceeded to capture Aphrodite A while in the Gool. While the plan to use Aphrodite as a hostage seemed to work even with the Kaiser being lifted up to the ship, the arrival of the Great Booster foiled those plans and Kaiser destroyed the Gool.
In the manga by Naoto Tsushima, the Gool fortresses were mass produced and faced off against the Kaiser and Mazinger Army before they were all felled save for a special model that was also a Mechanical Beast.