Rean didn't hear anything about the commotion inside. He simply pressed forward while waiting for the next formation to appear.
Most formations that used cores kept their flow of Spiritual Energy hidden. If they couldn't do that, the formation would be made in a way where the Spiritual Energy flowed evenly everywhere, preventing one from pinpointing the core's location. Or maybe the core would be protected by something.
After all, if the core of a formation that needs it was destroyed, the formation would become useless. It's common practice to make preparations for it to not happen. Naturally, the Formations Guild wasn't idiotic enough to leave it exposed. If anything, the Illusion Formation Core was better hidden than normal formations at the same level.
