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Prodigies were transgressions in the natural, predictable order of the cosmos – signs of divine anger that portended conflict and misfortune. The Senate decided whether a reported prodigy was false, or genuine and in the public interest, in which case it was referred to the public priests, augurs and haruspices for ritual expiation. In 207 BC, during one of the Punic Wars' worst crises, the Senate dealt with an unprecedented number of confirmed prodigies whose expiation would have involved "at least twenty days" of dedicated rites.

What did the expiation of a prodigy impose?
dedicated rites