The Feared Hero is a tome found in Act II of Diablo III, found in the East Stinging Winds. It will be in a satchel in a small camp randomly appearing throughout the area, amidst the Cultists.
This tome is required for the Eavesdropper achievement.
The parts read as follows:
We camp, lying in wait for a hero of incredible prowess. My gut churns with the suspicions that we are simply fodder. I have heard tales of this hero wading through our ranks, slaughtering us as if we were children. I will not sleep again tonight, I fear. — Dark Cultist