After Roland stormed into the hall, the "Legion" that filled the streets and alleys immediately withdrew, and the deafening lamentations of the mechanical undead subsided for a while. Yet starting an hour ago, for reasons unknown, the tower became inundated with an unprecedented chorus of undead sighs.
A completely different "sound."
The artificial intelligence of the "Legion" is a product of copying the neural circuits of deceased brains. While achieving intelligence, it retains the dying thoughts of the deceased at their final moments. The "sound" heard by magicians with special sensibilities is nothing less than the last whispers of the dead, trapped within these machines of slaughter—what might academically be termed "residues of existence."