Old peaceful city in desert.
Predicted their doom in their calender. Wanted to save something for the kids. Used arcane devices (cameras) to record a normal day in their life (in full 3-D).
Devices uses blessed water to store information, kept in urns. One for audio, one for visual.
City and people perished. All that's left in the ruins are urns with water (tapes) and large hollow craniums (playback devices). But the water slowly evaporated, distorting the information, making them nightmare versions of what really happened.
Pouring the water into the skulls will play the scenes in full 3-D (as a hologram).
They last about 30 sec - 2 min, and will repeat forever if not poured back.
25 % risk the recordings will become aware of the present, breaking through time and space. Depending on how distorted the information is, the beings in the recordings may react hostile.
A tall pillar stands alone in the center of the ruins. Carved ideograms on its sides tells the story of the now gone inhabitants (keyed version at the bottom):