William had read Lancelot's autobiography before. He believed that the Viscount of Light hadn't lied.
However, one should be vigilant at all times. He wasn't wary of Lancelot, but of the Viscount of Darkness and the dark creatures.
He was afraid that the butterfly effect would cause some things to change.
So, he had deliberately planted a small black snake on a dark creature with Epic bloodline. He wanted to trace the location at which the Blood Moon Dark Witch's resurrection would take place. He didn't expect that the place was really located under this library.
In William's previous life, Lancelot didn't have a chance to enter this underground space before the Blood Moon Dark Witch was resurrected. She had become extremely powerful in a short period of time.
In the end, the entire city had fallen prey to the Dark World.
William and the others had to enter now, before the Blood Moon Dark Witch became more powerful.