Sun Dasheng was indeed the key node linking the two worlds, but it was Cheng Tian's authority that constructed the Cross-Dimensional passage.
And the authority he drew upon came from the connection between the True Lord Erlang, Manifestation of Divine Power Template loaded by Cheng Tian and Erlang Shen's true body in the Black Myth world.
After all, they were fighting across dimensions. The Black Myth instance could not possibly allow the Three-Party Allied Army to swagger collectively into its world.
For example, the scarlet energy erupting from that spacetime rift was actually the Black Myth world's "firewall" at work.
But no matter how advanced its firewall was, it could not surpass the "Great Expedition" authority granted by the space and held in Cheng Tian's hands. It was practically like remotely taking control of the Black Myth computer directly.
Yet authority alone was not enough. They also needed to find a way to open a sufficiently large passage.
Using the firewall analogy, the three terabytes of data that made up the Three-Party Allied Army from Journey to the West: The Great Sage's Fury could not simply be cut and pasted onto the Black Myth computer's hard drive, which had barely a few hundred megabytes left.
Forcing the paste would mean that only a small number of units occupying less storage could enter the Black Myth world. Most would be blocked outside, and a careless operation might even result in lost data—in other words, deaths.
But through his authority, Cheng Tian quickly found a loophole in the Black Myth world: the Small World built around Mount Mei by Erlang Shen's faction, hidden within the mural of Futuo Tower.
This Small World was like an external hard drive with far more space. Not only could it accommodate the Three-Party Allied Army flooding