The three young geniuses were completely unaware of their ghostly pursuers. The staircase was eerie enough on its own. It didn't need their help to frighten them.
The darkness was lit by twin torches on the narrow walls. When the trio walked between them, they'd flicker with blue flames and reveal that there was far more staircase waiting for them than they ever expected.
It was a much longer descent than it needed to be.
Was it meant to destabilize their minds? If so, it definitely worked.
There was a haunting aura to each and every step. The further down they went, the more they felt like they were walking into the underworld.
The fact that they were together was a huge help. If any one of them had to do it alone, they might not have been able to.
Still, they took it step by step and eventually made it to level ground again.