The entrance into the inner sect was at the bottom of a lake. This lake was somewhere in the outer section. But it had been hidden so it couldn't be found without the sect ID card.
When they entered the entrance and came out of the lake in the inner sect, they had to be inspected again before they were allowed to leave.
But this time, the inspection didn't take long because some powerful people in the sect had come to receive Arthur. These powerful people didn't want to wait longer, and they could tell that he wasn't an imposter, so they cut the inspection short.
The three powerful people were one flying golem, one being made completely of lightning, and one green humanoid feminine plant. He had met the flying golem before, so he knew that the three of them were likely to be the current three patriarchs of the sect.
