 Naomi had actually survived Metatron's attack on her, and had spent the last years recovering.She then tells Castiel that due to the fact that there are only a dozen or so angels left alive after the various wars and purges of recent years, Heaven is at risk of falling apart and having the billions of souls residing there sent back to Earth as ghosts, which would cause untold destruction and chaos.She and the surviving angels must stay in Heaven in order to keep it running, although his news about an archangel, Gabriel, being alive gives them hope as his power could help keep Heaven running.