[Source] Count Enzo Etcheverry is a secondary character in The Witcher 2: Assassins of Kings. In order to successfully complete the achievement Eagle Eye you must aim dead centre at the soldier on the right, as opposed to aiming directly at Count Etcheverry. If you miss Etcheverry with the first ballista, then you encounter him later after destroying the gate with the ballista in the courtyard. He then drops a Fibre enhancer.