Greek religion, as seen in Homer's Iliad, is of a type known as "do ut des" ("I give that you might give"). Humans interact with the gods to attract divine benevolence and to ward off or propitiate divine disfavour. Three modes of human-divine interaction appear in the Iliad. the first is divination, whereby seers or diviners consult auguries and observe omens in an attempot to discover the will of the gods. The second is religious ritual or sacrifice by which humans attempt to offer things to the gods that the gods desire (smoke rising from the burned fat and viscera of sacrificed animals, e.g.) in order to obtain divine faviur. Finally, humans regulate or modify their behaviour to avoid divine disfavour. For example, in Iliad Book 6, Diomedes and Glaucus refuse to fight each other because they have a bond of guest friendship via familial connections and injuring one another would bring down upon them the wrath of Zeus in his aspect as the "god of guests/strangers". Use of divination and subsequent appeasement of the angry diety is the main theme of Book 1, in which Apollo has sent a plague because the Greeks seizing the daughter of one of his priests, diviners seek the cause of the plague, and the daughter is restored and sacrifices offered to end the plague.