That's the so-called Gate of Truth!
At that time, The Last Serpent was also very excited, thinking he was finally going to see the Dawn Devil that existed between the boasts of both parties, and from behind that door, came the strange tones of voices muttering something like "The infinite spirit and perfect life have finally merged"!
But before the door could open, a more intense battle broke out in the neighboring galaxy!
You see, at this stage of the "Civilization" game, the remaining civilizations are all top-notch players! Since the Holy Paladin was knocked out of the game by the Light of Hope, the God of Suffering temporarily took his place to play. During this time, the tensions between the remaining dozen or so Catastrophe-level civilizations began to escalate. The Magical Girl Vali called to arms, and suddenly the whole universe was in chaos!
