Sibˈyllist noun

A believer in the Sibylline prophecies

Sibylline Books plural noun

Prophetic books said to have been offered to the Roman king Tarquinius Superbus by the Sibyl of Cumae, of which he ultimately bought three for the price he had refused to give for nine, these three being held in the Capitol and referred to by the Roman senate in times of emergency and disaster (a later set was made after the first collection was destroyed by fire in 83BC)