The Jarjacha is a nocturnal Peruvian beast, quadrupedal, with a long neck and glowing eyes. It lives on a diet of human flesh, but has very specific preferences: it feeds solely on incestuous men and women, or those who have committed carnal sins towards their spiritual compadres. It itself may be born from the soul of an incestuous person or taboo-breaker.
A jarjacha manifests primarily in its call, a loud rattling cry that echoes through the hills. “Jar-jar-jar-jar-jar”… It repeats, over and over. The villagers shiver, cross themselves, and lock their doors.
By morning the atmosphere is tense. Everyone knows there is a sinner among them, some incestuous wretch who has brought judgment down on themselves. The parish priest decries the existence of the son of Satan in their midst, one who will be punished by divine retribution. Eventually the shamed culprit is brought to light, and given an auto-da-fé in the public square.
Jarjacha is the worst insult that can be leveled at someone.
References
Bustamante, M. E. (1943) Apuntes para el folklore Peruano. La Miniatura, Ayacucho.