Dimensional collapse.
"This… this can't be!" Nino said as she watched the distant Dimensional Rifts, her whole body shaking with horror. "We… had time… I was sure of it!"
Just like how the Aether from the human Souls served as bait to draw the Nephilim world's Primordial in, the Key itself became a beacon. The high concentration of the fifth element removed the need for the Ritual, an unintended consequence of creating such high grade Artifact which leads to its presence being detected by ancient entities from other plains and dimensions.