Thirty-four thousand years before the 24th century, during the war involving the Perikian Republic, the Endtree, the Bajora and the Lerrit, the entrance to the Fire Caves collapsed. The city of Yvrig was destroyed in the disaster, of which survivors said was caused by a blue fire. Kira Nerys theorized this was the Prophets imprisoning the Pah-wraiths there. (DS9 short story: "Horn and Ivory") Not all of the Pah-wraiths were imprisoned in the Fire Caves as others entered Jalkaree and Jalbador. (DS9 novel: The Fall of Terok Nor)