There are rumors that the Iron Hand still has access to a handful of plans for the WarMechs, and have been producing them by the masses in the effort to conquer the world. For all known accounts of them in battle, they have shown to be effective in that task.
We don't know too much about this breed of WarMech, only that those foolish enough to go against one have never returned. Direct footage is scarce and often damaged, and living witnesses are few and far between, so it is difficult to pinpont what and how one may work and fight, all that is known is that they are very large, and very dangerous.
Procede with caution against the Iron Hand. You may be unlucky to go against one of these monsters yourself.