The Harvester in some ways is more feared than the Walkers. While the Walkers may vaporize entire cities, the Harvesters are sent in to gather the remains and "study" them. Their methods are cruel and agonizing as pain relieving drugs are omitted. They are piloted by a single alien, but often arrive in packs of fifteen or twenty to scavenge a city. By a combination of Walkers and Harvesters, the known population of New York city was wiped out or captured in a less than three hours (no offense to those of you living in New York :P)
About this creation
The Harvester with its tools fully deployed. The vehicle is also outfitted with two small guns that always point forward and one small gun that's mounted over the shoulder that can fire in any direction.
Here you can see its thrusters exposed and firing.
A rooted mode similar to the Armageddon Walker except this time it is for science!