Sareth was not stupid. After hearing what Cerberus said, his eyes rolled, and he immediately understood.
Cerberus said that its demon contract was in Mundus's hands, and according to Sareth's investigation, this possible demon king named Mundus seemed to have been sealed by Sparda. However, being sealed meant that he was not dead. In other words, Cerberus's demon contract was still in effect, but Mundus could not give it any orders now. Thus, when Demon Lord Urizen appeared, Cerberus had to obey Urizen's orders temporarily due to his strength.
It was only obedience, not allegiance. Perhaps in the eyes of Cerberus, Urizen was still inferior to Mundus… This led to Cerberus having its own ideas and actions despite being sent out by Urizen to investigate.
"In other words, we're not enemies?" Sareth probed.
