Behind Celestial Virūpākṣa were streams of divine sense, which belonged to the other celestials in the city, all of whom had detected what was occurring with the spell formation.
Most of them intentionally hung back a bit. After all, Bai Xiaochun had just killed Celestial Deadfall and seriously injured Reverend Devourer, leaving all of them quite shaken.
Some, such as Prince Ur-Demon, were so frightened that they only dared to send out divine sense, and even then, let Celestial Virūpākṣa take the lead.
Celestial Virūpākṣa, on the other hand, was the strongest celestial in Vile-Emperor City, and had long since come to hate Bai Xiaochun. He had become suspicious of him back when they were both on the damaged fan, and had also suffered at his hands during the incident with the sovereign clone. Therefore, he did not hesitate at all to intervene when Bai Xiaochun tried to break open the spell formation.