The Sealed Light Breaks I
The Luxera that the Goddess of Light Luminaria started to flood out of the crack. She was already initially sealed for eight days when this happened. The crack started spewing light monsters at the ninth day. It would have been fine if this was just the case, but the crack became bigger which spewed bigger and more powerful Luxera.
If the Luxera that came out did not try and make the crack bigger, then it would have been fine. Even if the effect of a small crack was unnoticeable, the fact that multiple Luxera pounded on the crack meant that the seal cannot hold its structure until the intended date. The crack became unstable to the point that even the dragons cannot tell when it will be released.