After making a rough guess of César's motive, Roy immediately understood why Demon Lord Rogeros had him continue carrying out the execution mission.
Logically speaking, even though he had sensed the Balotan Pillar, which had lost its functionality, had reactivated and came over to take a look out of curiosity, he actually did not have to expend a large amount of magic power to forcefully locate César's position and open the Gate of the Abyss. Roy had thought that this might have been because Rogeros was vengeful and could not tolerate any betrayal, so he was determined to kill César.
But in fact, after hearing Roy's story, he had probably realized what César wanted to do!
After all, the demon lord was a demon lord. These demon lords had lived in the Abyss for countless years and had seen many things. Any action was enough to make them think of the possible subsequent consequences.
