The others had guessed right. It really was Batman who had cut the power supply, shutting down every mechanism in every stage.
When they had entered the Central Energy Room earlier, he had wanted to do just that. But that Energy Hub had an extremely tight protective shield around it, basically a huge block of iron. Who knew who the stage designer had been guarding against; they had left absolutely no room to operate.
Of course, now everyone knew who he had been guarding against. Unfortunately, it had not guarded against him at all.
Batman had chosen not to touch it then because there had still been a chance of clearing the stage through the normal process. Batman was the kind of person who, if he was the one making the sacrifice, would not hesitate, because that was the most efficient way; but if he no longer had anything left to sacrifice and someone else had to be sacrificed, then he might temporarily abandon his lawful methods and use his intellect to exploit a loophole.
Now, Batman could no longer take part in the normal clearing process. Whoever needed to be sacrificed during the clear had nothing to do with him anymore. Under these circumstances, he would not care about the normal process. He would go straight for the core of the vital point and take down the most important part first.
After confirming that the Dungeon basically had no magical elements, it did not matter what mechanisms had been designed. Once there was no electricity, none of them could make trouble. So he simply cut the power, and the problem solved itself.
Of course, he had also considered whether directly cutting the power might cause some dangerous mechanisms to drop. But Batman had already noticed that the previous stages