Sacred Plaques

Most holy of all the wondrous relics the Lizardmen guard are the Sacred Plaques. Each plaque is wrought from gold, a substance chosen not for its value but for its longevity. Cast upon each plaque is a series of glyphs, the written language of the Lizardmen, describing an event that occurred in the past or has yet to occur in the future. Future events described on the plaques are treated as both prophecy and instruction. If an event is described, the Lizardmen will ensure it comes to pass, at the prescribed time. Each temple-city maintains its own sequence of plaques, yet non have possessed a complete sequence since before the Great Catastrophe.

Source
pg. 61
 * Warhammer Armies: Lizardmen (7th Edition)