Billy decided to make a low-budget version of the previous mirror and told them to use it. They confirmed that they could see the exact actions that they took before arriving at that place. However, it costs a lot of mana.
"We have two options," Billy said after returning the mirror. "Focus on learning about the past using Temporal Vision or use our mana to forcefully create a dungeon core here. Come to think of it, I can make a mirror powered by a core that will show the past and keep moving even further as it absorbs mana. So, we don't have to choose between either."