Terror-Beasts are daikaiju (Large Mysterious-beast) used by the evil Garoga's to attack planets in order to either take over or destroy them. Although they normally prefer more covert ways of taking over worlds they will fire a Terror-Missile if the plan isn't working and try to take a world by force. These missiles will either explode in which case the monster will parachute on the way down or will embed in the ground before exploding and unleashing the monster. There are several types of Terror-Beasts.
1. War machine or mecha's that are programmed for the mission.
2. Monsters that are converted into cyborgs for the mission.
3. Monsters that are made for the task. Including those that were experiments; Such as Dorola.
4.Monsters that were captured and controlled to carry out the mission such as Gigan and maybe King Ghidorah.
5. Garoga's that combine/fuse and transform into Terror-Beasts. In the case of Grotogauros.