Board Thread:The Panopticon/@comment-27350284-20151205202907/@comment-1789834-20151209111749

168.1.75.19 wrote: What I don't understand, something I am yet to find an answer to, is how could he chisel away at the wall over the period of 4.5 billion years when the entire castle resets itself every time he confesses/starts the struggle again? I think it's suggested that most, but not all, rooms are reset. For example, if all rooms were reset, then there'd be a bit of an issue with the skull and 'BIRD' in the teleport room. They'd both disappear and then the Doctor would never get his inspiration to tell the story while hammering the wall (and the skulls would never fall into the ocean). It could be assumed that this is the Time Lords' doing. They know the Doctor is stubborn and would need persuading, so allowing him to see all of those skulls building up and reach the conclusion that they are all his own would frighten him.

In summary, it's clear that not every room resets, and it's a wise to reach the conclusion that the Time Lords intended this to happen in their attempt to know more about the Hybrid.