Shilen's Stone Statue:
Currently the magic power of Sailren and its followers is very strong. I do not think you can win solely with your own power, especially given how weak the seal stones have become.
My counsel is that you first recover the power to seal and wait 'til Sailren's strength lessens a bit. Then you will have your best chance of entering the nest and defeating this ancient evil.
Listen to the entry requirements and battle method.