In an era of planetary shields, the easiest way to conquer a world is to put boots on the ground. But even the largest army of surface troops can be neutralized by hostile or impassable terrain, which is why the Eternal Empire developed the world thrasher.
A massive armored vehicle, world thrashers are sent to clear a path for incoming ground troops during the first wave of a planetary invasion. These automated machines of environmental destruction can uproot or incinerate trees, smash boulders, flatten hills, and even burrow through mountains, earning them the nickname "death tractors."
Attempts to utilize world thrashers as weapons have failed because their bulk makes them too ponderous and slow to effectively keep up with a military advance. However, any enemy soldiers careless enough to approach the death tractors will inevitably suffer heavy casualties.