Yes gentlemen, I think it worthwhile to consider the Hydra as a foe. You say no creature of Chaos is predictable, yet I submit that they are as stable as any beast so subject to mutation can be. Times being as they are, our brave soldiers may soon face one or more of them on the field of war. You have asked me to uncover the weaknesses of that which you may fight; should you confront a Hydra, your target lies within its torso. Every parcel of information that I've discovered convinces me that their large central trunk is what truly holds the Hydra's brain. How else could its many heads function in concert, with no great loss of function if several are destroyed? Each may certainly have a vestigial intellect, but the central controlling mind is in the body. Unfortunately, the organ that ignites their fiery breath lies as the junction of their necks, close to the brain and the spot is, naturally, very well armoured in scales. I strongly suggest that our artillerists aim for the front and centre of the torso, as nothing else short of a full charge by an armoured knight will penetrate that armoured hide over that most crucial of spots.