Meet All, an anomaly (sort of like Cross, but not exactly). This anomaly occurred when all of the DANG CHEMICAL POLLUTION THAT WE PUT UNDERGROUND finally reached the CORE. This caused the CORE to glitch while exploding. Frisk, Sans, Papyrus, Grillby, Undyne, Asgore, Flowey, Asriel, Toriel, Mettaton and Alphys had rushed over to see if they can stop it, but as a result.... they failed. The CORE exploded, setting the underground to nothingness. In addition it had merged together the ones that went to the CORE into one being.... All. I know. Boring story. .-.