Dong Santong had no choice but to agree with the Divine Light Roc's suggestion. If everyone else agreed to act while he alone objected, the other Demon Kings would naturally resent him. After all, it really was an excellent idea...
Because...
With all the Demon Kings and Demonic Cultivators banding together, they presented far too large a target. There was no hiding from Li Xiaoya and the other cultivators...
In a head-on, one-on-one fight, they stood little chance against the Immortal Race Cultivators. Their only option was to join forces against them... And the Devil Race was hardly a dependable ally, either...
Just as the Divine Light Roc had said, if these Demon Kings built a sufficiently large defensive city or fortifications, the Bright Star Realm had more than enough Demon Beasts at the Immortal Tribulation Stage and Mighty One Stage to mount a powerful joint defense. With that, the Demon Kings would only have to hide inside and strike when needed. Things would become much simpler for them and their Demon Beasts...
The Divine Light Roc's proposal to build fortifications, regardless of how the city itself turned out, was actually an opportunity to establish a racial structure of their own. If they successfully weathered this trial by the Immortal Race Cultivators, the city jointly founded by the Divine Light Roc and the other Demon Kings might someday give rise to a new race...
In fact...
The cultivators of the various races across the Greater Star Realms had generally evolved from Demon Beasts, and most had undergone a similar process... But too much was involved in that, and Dong Santong did not understand it very well...
Still!
This certainly revealed the Divine Light Roc's lofty ambitions...
Of course, if the city really was established, it would indeed put Dong Santong