Theory:Doctor Who television discontinuity and plot holes/Heaven Sent


 * The obvious one. If all the rooms in the castle reset - how is the Doctor able to slowly wear down the diamond wall over multiple incarnations?
 * At a guess the resetting stops when the Doctor 'dies' and begins again when he 'arrives'. So the settings are as they were when he begins the loop again (all the rooms would have been rest by then to their 'normal' settings). The diamond wall room is occupied when the Doctor dies so the resetting stops when he has done some damage and stays that way until the loop stops with him inside it again. You may ask why, if this is true, do the bloodstains on the floor dispensary, to which I can only answer that maybe the floor is independently self cleaning?
 * But the rooms reset if the Doctor leaves for sometime, but i think if this material is harder than diamond is also hard to regenerate.


 * Every 100 years the bird (got from the writing in the sand) pecks at the wall, therefore what the doctor is doing is pointless.
 * The writing "bird" in the sand is meant to remind the Doctor of the story. There is no real bird.


 * Who put the very first costume in the fireplace room? or the first 12th doctor just put off the wet one, left it and went on naked? otherwise there'd be no extra costume for the next 12 and why didn't it disappear when the room reset? even if it's not supposed to be gone because it's like a part of something alien-not-castle-stuff, still the question stands - who put the first costume in the room?
 * The most likely answer is the one you give in your question - The Doctor takes off his clothes (possibly leaving on undergarments, as we don't see those there) to dry by the fire. He then goes wandering about, eventually dies and brings in a "new" Doctor. When he gets wet, he finds the previous set of clothes, and swaps them out. The cycle then continues.
 * What OP means is where would the clothes have come from the first time the Doctor came. This is a good question -- the Doctor finding his clothes there suggest that those are the clothes left by the last Doctor. Thus perpetually the Doctor is putting his clothes there and picking up the wardrobe of his predecessor. But if there were no clothes the first time, the Doctor would and could not have left his clothing there. Various things could explain this tho. There could have been extra clothing in that room and the loop would still work, as this room clearly is one of the ones exempt from the reset. So a clown outfit could have been there and the room wouldn't put the clown outfit back because it doesn't reset. Or maybe there's clothes hidden elsewhere in the room that the Doctor doesn't find in all cases past the first one because he doesn't need to. Or possibly the first time he stripped his clothes down without another wardrobe and spent the rest of the episode after that point naked. I prefer the later possibility, and will now accept it as head canon.
 * Thanks for the answers, except I think the costume room does reset, as otherwise the fire in the fireplace would've gone out many years ago. I do like the idea of him finding some other clothes somewhere in the room or the castle (there was a bed, and food, could easily be a wardrobe too), and as you said, after leaving his own costume there for the first time, he never needed any other clothes to look for. And the costume doesn't reset because it is indeed something that the Doctor brought with him, foreign material and stuff. Seems legit for me.


 * What was the point in taking the panel from the floor, writing on it and burying in the garden? and if all the rooms except the wall one reset, why the garden and the floor didn't? The garden only resets to the grave being dug up back again, but that's not what it was like when the Doctor first got there. Or in fact he wasn't who dug it, the Time Lords were, so the dug up grave was a default? Why? To show him the way? But why so complicated?
 * See point above above he bird pecking on the wall every 100 years.
 * Sorry, still not getting it. The bird and 100 years is just a metaphor, in fact the Doctor every time beats the wall as often as he can. How does this answer my question? And what the Doctor is doing is the opposite of pointless, the problem is eventually solved exactly because he's been doing it for all this time. And if you mean that all other his actions are pointless because of resetting, I still want to know who dug the grave and depending on this why doesn't it reset.
 * If the moment a new Doctor clone is created the base state for the reset is made. That would solve the problem with the word bird not disappearing from the sand.
 * But not the Wall which i have two theories:
 * 1)The Wall room is non-resettable
 * 2)The Azbantium is too difficult to be "reset"
 * I think the first one is correct, if the TimeLords wanted it to be reset, they would made the wall of something more 'resettable'. I think they had no idea he'd do something like what he did, and as the wall was actually a gate of sorts, they never intended for it to reset - no need, it's not even technically a part of the castle.


 * If the rooms reset all the time, why the word 'bird' stayed on the sand for a while for the Doctor to read it, and was gone later? And why the castle started moving and opened a way to the roof when the Doctor saw this word? The Bird clearly means no good for the Time Lords, more like vice versa.
 * The doctor writes the word 'bird' when he is week, each new doctor reads it and wipes it away. When the room is reset the word is written there for him the read.
 * Both questions stand, why doesn't the word reset as everything else and why the way to the roof opened exactly when the Doctor saw the word. As initially, when the Doctor first arrived there (which is, as i understood, the state that the rooms are supposed to reset to) there couldn't be any such word, as there was no Doctor yet to write it.
 * The hypothesis above suggests that the reset value for the room is determined when the "new" Doctor arrives, or even as the "old" Doctor dies (being before the word has disappeared).
 * As for the bird thing, i now think that the Doctor's ashes it what the Doctor's basically become, it's a significant part of him, which can't be reset by the castle, which is why he chooses it to leave a message. And well, also because there's nothing else he can possibly reach at that moment. So no matter if the Doctor leaves the room or not, the word stays and it's blown away by the wind later.


 * The castle in the state presented in the episode is made up out of a mixture of bread crumbs left behind by the Doctor (and for some reason not reset to the default), bread crumbs(?) that are a default part of the castle and just random stuff and it's not always obvious which is which. What is clear, though, is that the first time (and possibly a few more after the first one) the Doctor is transported there differed from the sequence occurring ad nauseum in the episode. At what point did the Doctor set up the scenario as we saw it unfold? How much of it was actually set up by him and what parts were already part of the default castle? Also, how was the transporter activated the first time?
 * The Doctor had 7,000 years worth of attempts to setup the bread crumbs before we first join the episode. As to the first activation of the teleport, that presumably was set to occur after he was sent away from Ashildr in the previous episode. Each "burned out" version of the Doctor just needed to activate the special rematerialisation of the stored pattern.


 * Why, for God's sake, doesn't the Doctor figure out something better to hit that wall with than his hands?
 * Put yourself in his position. If you were trapped inside that room with the Veil coming at you, how else are you going to go back and get that other thing to hit the wall with? Furthermore, I doubt using that other thing would actually get him out of that area faster


 * At the end we see everything took place inside a confession dial, but was it the Doctor's confession dial? If so, why was this what was inside it and shouldn't he have known?
 * Perhaps the dial was meant to extract the confessions out of the Doctor


 * Once on Gallifrey the Doctor casually reveals the secret he was so insistent not to reveal to the Veil just moments earlier. So why did he go through the torturous process of creating and sacrificing billions of clones?
 * Dialogue states he knows of only the legend of the Hybrid and he did state, just before he punched through that hard wall, that he would no longer be confessing to the Veil his knowledge about the Hybrid - which of course included the confession we heard at the end.
 * But the point was, apparently, not to not confess specifically to the Veil, but to not confess at all. I think the whole point of keeping the Hybrid secret was to protect Gallifrey. As he had no idea that the Timelords were those who tortured him (if that's true, things still can be not what they seem), he wanted to protect them and not to let the unknown torturer to learn the secret that he can use against the Timelords. And later, of course, when he realized it was all in vain and they were the ones who tortured him to find out the truth, and they were the reason Clara died (seriously, she was partly the reason of saving them, i hate those guys and would be glad if in the finale it's revealed they're actually innocent), he had no desire to protect them any longer, and thus revealed the secret with a quite clear warning about what now awaits them for everything they've done.


 * This is point four: Too many skulls. In the water the Doctor sees many thousands of skulls. He emerges from the water in the interior of the castle. Billions of skulls being added would eventually inundate the castle. The depth of the water within the castle walls can be estimated. 7000 years in the future gives the point at which we join the story. If he survives in the castle for a week, 52 skulls a year will be deposited. 7000 x 52 = 364,000 skulls.This amount does not rise above the water in the interior of the castle. If he adds the same amount until breaching the crystal wall he will add 104,000,000,000 skulls. The castle would overflow with skulls. Even if the skulls fall exterior to the castle the 'angle of repose' applies. Complicating factors such as currents, storms and the depth of the water exterior to the castle all lead to the same conclusion: too many skulls.
 * You have to remember that skulls don't last forever. They'll eventually turn to dust, allowing for newer skulls to take their place.
 * Indeed. Considering that the Doctor appears to live and die at a consistent rate by the time we hit this episode, the bones would decay and add up at a consistent rate leaving a perpetual collection of skulls.