Furies were the daughters of the night, created from the blood of the murdered. They manifested as sandstorms or whirlwinds in order to kill those who had killed others. As daughters of the night, they would not attack during the day, but would manifest themselves to trail their prey. They could only be summoned when an individual called for them, and they could only be stopped if the one who summoned forgave the murderer. Arcas once called for them while journeying to Helios. He asked that his father be avenged as he believed Otus, who was travelling with the group, was responsible. (The Furies)
In Greek mythology the Erinyes (/ɪˈrɪniˌiːz/; sing. Erinys /ɪˈrɪnɪs/; Greek: Ἐρῑνύες [ῠ], pl. of Ἐρῑνύς [ῡ], Erinys), also known as Furies, were female chthonic deities of vengeance; they were sometimes referred to as "infernal goddesses" (χθόνιαι θεαί). A formulaic oath in the Iliad invokes them as "those who beneath the earth punish whosoever has sworn a false oath". Burkert suggests they are "an embodiment of the act of self-cursing contained in the oath". They correspond to the Dirae in Roman mythology, and some suppose that they are called Furies in hell, Harpies on earth, and Dirae in heaven.