Machines
The benefits of having Machines as part of your Army in Nightmares RPG can be discussed here.
The following standard percentages apply:
Att:50% Dam:100%
As you can see, Machines are slaughterers with 100% damage each time. They are very expensive though, so it is not likely they will be a common piece on the battlefield. However you should glance over an opponent's Army to ensure none of these are within the ranks.