History Headscratchers / DoctorWhoS35E11HeavenSent

* Why is the ocean floor covered only with skulls? Shouldn't it be covered with both skulls ''and'' benches? (and broken glass?)

** Since "[[Recap/DoctorWhoS1E5TheKeysOfMarinus" The Keys of Marinus]], that was the first time he was seen to teleport.

[[folder: The buried clue]]
* Why did the Doctor leave the "I am in 12" clue buried so deeply (or at all)? I considered that maybe it was in an attempt to circumvent the whole "resetting" thing, but the chalk arrows pointing to the burial spot didn't reset, so why not just leave it at surface level? Also, why not mention something like "take the spade to 12"? Surely having a metal implement would shave off a few million years.
** Presumably "I am in 12" was the only thing he had the time to write before the monster caught up with him? Since we don't see the Doctor write those words during the loop that repeats in the episode, it must've gone happened in an earlier iteration where things went differently. Presumably in that iteration the monster could've appeared at any point while the Doctor was digging the grave and writing words, so he decided to keep the message as short as possible so that he would have the time to write it.
*** But still, why bury it? That takes a lot more time than just scrawling a message.
*** "Hell Bent" explains this. The Doctor has to keep the Time Lords believing that he knows what the Hybrid is, so some events needed to repeat with each cycle until he could punch through the wall. One of them was his declaration of why he left Gallifrey which only happened because the Veil cornered him while he was digging in the grave. He couldn't bypass it.
*** Things inside the castle revert, things outside of it don't. Presumably by burying the slab in the soil ''beneath'' the castle, an earlier iteration of Twelve managed to LogicBomb the reset mechanism, presenting it with something (that particular flagstone floor) which was both inside ''and outside'' the castle at the same time.

[[folder: More on Room 12 vs. the rest of the castle]]
* Why is Room 12 the only part of the entire castle that doesn't reset with each cycle?
** Probably the individual rooms are designed to re-set themselves just before he returns to them. He never ''returns'' to Room 12: his next copy does.
** Everything ''inside'' the castle resets. Things ''outside'' of the castle do not. Hence, the skull which falls into the water escapes the reset. If it had fallen the other way, it would disappear each round. What is labeled as "12" is actually the way ''out'', that's the whole point of it. What is beyond that super-wall is outside of the castle, and apparently the "outside" area begins at the start of the wall.
* So given, by the end of it, the Doctor has done this billions of times. At minimum two billion, assuming he spends a full year in the castle each cycle which is quite generous, it's probably closer to a week or month. We see an entire lake full of skulls the first time we go through this at 7,000 years into the future. A billion is a really big number. Surely, by the time the Doctor gets that far, the lake would entirely fill up with skulls, thus eventually killing him when he lands on a compressed bedrock of skulls instead of the water. There's also the little issue that he seems to be getting more energy out of repowering the teleporter than he's putting into it. Each time the Doctor goes through it, he's creating a new skull. So either the Doctor should be getting weaker as the cycles go on, or the process is violating the law of Conservation of Mass/Energy.
** The skulls wear out and disintegrate from the weight of the ones above them as fast as he's adding them. The waves wash the bone dust away. As for the energy issue, who knows how much energy might be in his body when it's trying extremely hard to regenerate, but can't get the process started because it's too damaged? Surely enough to remake a body, because that's what it's normally used for.
** For that matter, shouldn't the skulls be intermixed with thousands of stools, broken glass, and bits of window frame? All of those things also fell into the water every cycle.
** The window and the chair are part of the castle's furnishings. They probably re-set no matter where they're moved to. After all, the castle can't afford to have one Doctor throw the shovels out a window and force all his successors to dig with their bare hands, can it?

[[folder:Required time]]

* How long would it really take to punch through a wall ''20ft thick and 400x tougher than diamond''? Assuming the rate of the few punches he does, every 2 days...
** FridgeBrilliance: The wall wasn't actually Azbantium, but a manifestation of ''the Time Lock'' that keeps Gallifrey cut off from the universe. The Doctor's status as a Time Lord has previously allowed him to physically bull his way through Time-based obstacles, as per his ability to move with great effort when time was frozen in "Invasion of the Dinosaurs". In this case, that ability to ''force'' one's way through such barriers was exploited by the Confession Dial to ensure that '''only''' a legitimate Time Lord could break through, albeit in the cruelest way possible.
** Also, remember what the Half-Faced Man said in Deep Breath? The Doctor, like all Timelords, is stronger than he looks.
** Don't forget the effect that sheer time has on any substance. In two billion years even diamonds would turn into dust from nothing but contact with air. It's possible that the substance was growing increasingly brittle as the Doctor went along.
** His obstacle was a six-meter thick wall and he faced it about 300 billion times. This means that each time he had to wear out 20 picometers (20 * 10^-12) off the surface by average. Combined with his bounding box, that comes as about 0.018 cubic millimeters of the crystalline material, each iteration.
** Plus due to the gaining distance, progressive iterations would have more time to punch more.
** And probably more enthusiasm, as they'd be able to see clear evidence that he's going to make it eventually.
** The best guess of the Sisterhood is that the Doctor was inside the dial for 4.5 billion "years," as indicated by the simulated sky outside the simulated castle, and always remembering he has no memory of previous loops, starting each loop with the same body and the same memories. Assuming the Doctor reaches room 12 every two "days" of the simulated "years," that's 821,812,500,000,000 punching events. Call it about 822 trillion.

[[folder:Second of Eternity]]

* The king asked "How many seconds are there in eternity?", not "What is a second of eternity?". And whether you use those special seconds or just plain old seconds, shouldn't the answer to the king's question be the same? There are infinite seconds in eternity.
** The point to the shepherd boy's answer isn't to give an actual number: it's to express to the king that counting off seconds is irrelevant to the "eternity" concept. ''Any'' finite amount of time, whether an actual second or the eons it takes the bird to wear down the entire mountain, is inconceivably brief from the perspective of eternity.

[[folder:Portrait]]

* Did Clara's portrait show its actual age, despite the bedroom's reversions? The Doctor judges it to be "very old" when he examines it in the first iteration shown, and a later shot when he's moving from room to room gave a glimpse of a chamber with empty picture frames on its walls. If so, did his later iterations only see an empty frame and a pile of disintegrated canvas dust which isn't a bad reminder of her absence in itself...?
** An earlier Doctor may have painted it.
*** The fact the Doctor painted the portrait was confirmed by Steven Moffat in an interview published in ''Doctor Who Magazine'' #495.

[[folder:Confession dial workings]]

* So the Doctor was teleported into the Confession Dial. He told Ashildr in "Face the Raven" that he didn't know how it worked, and it was said earlier in the season that it could only open when he died. What was the point of the castle if the dial didn't actually contain the Doctor's confession? Why would it have contained a fragment of the Time Lock capable of being destroyed by the Doctor and the Doctor alone? Why would the Doctor have given the dial to Missy, if she couldn't have used it to get to Gallifrey (and it didn't have his confession ready to be played)? How did the dial itself get to Gallifrey from Ashildr (since we see it open to let the Doctor out at the end of the episode)?
** Possibly the dials are normally used to create a captive copy of a Time Lord's personality, whose intellect can be transferred into the Gallifreyan Matrix upon their final death. Each dial would need a communication-link to Gallifrey to do this, and the true nature of the dials would be kept secret from all but the highest-ranking Time Lords to ensure that link couldn't be exploited to hack the Matrix. When Gallifrey became Time Locked and trapped in its pocket universe, the link to the Doctor's dial got blocked by the crystalline wall, so instead of having to work his way into Room 12 just once, the Doctor had to ''punch'' his way in. The castle, Veil, and mechanisms were all custom-generated to drive him into Room 12 and goad him into entering; the fact it took him several billion tries was an unintended consequence of the blockage being there. By the time he managed it, his confession dial had been brought into Gallifrey in the same way that the white-point star diamond got ''out'' of the Time Lock for "The End Of Time", and had been adjusted so that it'd construct yet another copy of the Doctor's body for him to occupy there as he stepped through the link, instead of dumping his disembodied mind into the Matrix. Alternately, there are actually ''two'' copies of every confession dial: one to be carried by the Time Lord it belongs to, and another left safely behind on Gallifrey, both of them linked to the same BiggerOnTheInside pocket reality. As for why the dial requires confessions, it's to prime the deceased Time Lord personalities to give up all their secrets to the Matrix: something they'd otherwise be reluctant to do.
** The answer from "Hell Bent": the Confession Dial is designed to give dying Time Lords a chance to live peacefully and get whatever they need to off their chests before they're uploaded to the Matrix. The Doctor is rather angry that it was used to torture him into giving up information. Gallifrey escaped the Time Lock/pocket Universe on their own at some point offscreen, and the Dial was brought there so Rassilon could hear his confessions.

[[folder:Killed by the Veil]]

* When the doctor is killed by the veil, why doesn't he regenerate?
** Is there any actual death involved? Or is the castle, the veil & the transporter a tailored, repeating format the dial uses to elicit confessions. If so, is that how the dial usually works or are the Time Lord council using it to find the Hybrid?
** Time Lords are capable of stopping themselves from regenerating, like the Master did in "Last Of The Time Lords". Given the Doctors plan required him to return to the transporter room and create a new copy using his life energy it's likely that he stopped his regeneration on purpose.
** Except if he ''could'' still regenerate, doing so would have been the logical course of action: he'd have had plenty of time to come up with a better way to break through the wall than punching it, because the Veil'd disappeared after it grappled and wounded him. Instead, he muses about how Time Lords take a long time to die even when wounded too severely for regeneration, suggesting that's the state he's in.
** Did you miss the entire speech that he gave at the end? There are some deaths that even regeneration cannot cure. The body tried but it simply could not.

[[folder:Location of the dial and the teleport]]

* When the doctor transported at the end of "Face the Raven", was he sent into the dial which was itself sent to Gallifrey or was the Doctor sent direct to Gallifrey and his confessions given at some other point (the recording being in existence since "The Magician's Apprentice")?
** The bracelet probably transmitted him into the dial. He did say that the maximum range for a long-range teleporter was about a light-year, and Gallifrey was a whole lot farther off than that, even ''before'' it got dumped into another dimension.
** That bracelet is probably very similar to the one Missy used in series eight.

[[folder:The Doctor making the Confession Dial]]

* Let me see if I've got this right: The Doctor made the Confession Dial, then someone or something made a deal with Ashildr to trap The Doctor inside his own Confession Dial, and then The Doctor broke through it into Gallifrey. Who's plan was this? Did The Doctor set up this insanely elaborate plan and then erase his memory in order for it to work? If he knew how to get to Gallifrey in the first place, why set any of this up? Or was this some plan somehow set in place by The Timelords from within the Time Locked Gallifrey?
** The Doctor notes to Ashildr that he has no idea how a Confession Dial ''actually works'', implying that he didn't build his own. Keep in mind, the Time Lords sent a message back in time into a child's head to get out of the Time Lock on the War, Rassilon sent the Master a White-Point Star from within the Time Lock, and they were able to send regeneration energy through The Crack on Trenzalore - in short, they're locked up, but not powerless. The functions of the Dial may very well have been engineered by them at any point before (or after, since they're big on closed-loop paradoxes) their return to get them out of the lock, and sent back in time to the day he picked it up.
** Indeed, so far as the Time Lords know, the Doctor's the only one left who might still ''want'' to bring them back, now that the Master/Missy knows how they'd been exploiting her since childhood. They're hoping he can manage it before the silly sod gets himself killed, but can't count on that given how dangerous his life is. It's very likely that they rigged his Confession Dial to ensure that if he died, he'd be downloaded into it Nethersphere-style and have one last posthumous chance to penetrate the Time Lock. Then they lucked out, and managed to manipulate Ashildr into transporting him into the thing while still alive, same as Missy could visit the Promised Land via her own bracelet.

[[folder:Grave confession]]

* What was the Doctor's confession at the bottom of the grave? He realized that the Veil wouldn't kill him if he confessed, and stated "it was a lie, it was always a lie"; everything he said before that was too quick and... Scottish... to comprehend.
** He said he hadn't left Gallifrey because he was bored, he left because he was ''scared''.

[[folder:The Veil as a threat]]

* So, was the confession aspect of the trap just an ExcusePlot or did the creator of the whole scenario actually expect to get to know something about The Hybrid as a result of it? The Veil actually does very effectively kill The Doctor on contact, so it's a genuine threat - but it's actually too much of a threat to be useful as a torture mechanism (since The Doctor only has to resist once before, well, dying). The general theorisation here is that The Point was to get The Doctor to break through to Gallifrey, but this seems like a needlessly complicated way to do that, as well (why have The Veil be this deadly if you want The Doctor to act most effectively to get through that wall). This feels more like it's actually intended as an existential punishment device, rather than an effective means at either of the two previous ideas...
** Which also leads to the thought - who hates The Doctor enough to do this to him? The Doctor has previously mentioned that nobody hates him as much as he hates himself...
** Or someone wanted him to be very pissed off when he finally got to Gallifrey.
** Or someone just plain didn't have any ''other'' way to get him there, and needed him to do so no matter how much it hurt or angered him.
** "Hell Bent" provides the answer: Rassilon wanted to know what the Doctor knew about the Hybrid, and didn't actually anticipate him spending four and a half billion simulated years chipping away at a diamond wall with his fists.

[[folder:Spilling the secret at the end]]
* So, the Doctor is so determined not to reveal the truth about the Hybrid that he endures two ''billion'' [[note]]thousand million for those using the long scale...it seems implausible that they'd jump from hundreds of millions to millions of millions quite that suddenly[[/note]] years of repeated torture and death....and as soon as he escapes the trap meant to force the truth out of him, he just spills the beans for no apparent reason?
** They just spent billions of years scaring him to death. Now that he knows it's the Time Lords who were behind it, why wouldn't he want to return the favor?
** Because all the reasons why that secret could never be told should still apply just as much at that moment as it did one minute earlier when he was punching the wall.
** He couldn't tell them then because he wasn't ''on Gallifrey'' yet. If he'd admitted it while he was still trapped in the castle, they could've dumped his Confession Dial in the nearest trash-disintegrator and checked "Avert the Hybrid menace" off their To-Do list. Now it's too late: he's arrived, and their plan to identify the Hybrid has only succeeding in ''bringing'' him there, implying the prophecy is fated to play out despite their best efforts to stop it. And they'll '''know''' that.
** He may be lying through his teeth. There were *two* Time Lords of questionable provenance connected up to the Cloister Room during the [=McGann=] film, and the only other evidence of the Doctor being half human comes from the Doctor's own lips (pathological liar) and something shown to the Master by the TARDIS - who would probably quite cheerfully lie to the Master as well. Russell T Davies- admittedly, no longer in the driver's seat- has always maintained that a) the [=McGann=] film is canon, and b) the Doctor is ''not'' half human. Perhaps the closing line is not so much a confession as it is "Right, now to scare the Time Lords silly by telling them the Hybrid is coming for them, to keep them off the scent while I try to figure out what the hell to do about the *real* Hybrid...
** He is doing it for dramatic effect, to convince any eavesdroppers that he really does know. But he slips the sonic sunglasses on just before speaking the last two words. Maybe he's deliberately using the sunglasses to generate some kind of interference field so the eavesdroppers can't hear the last part of what he says.
[[/folder]]

[[folder:Repeating the loop]]
* In the billions of years that the Doctor is there does he do anything slightly different each time he is there like turning left instead of right?
** Possibly the first few iterations didn't get far enough to reach Room 12, and had to crawl back to the entry chamber without ever seeing the crystal wall. But as soon as one of him happened to win through, the others to follow would do exactly the same thing each time, because his previous selves had left the necessary help (BIRD, dry clothes) for him to solve the puzzle. From that point, all his iterations' lives were pretty much the same, because they all have the same mind and make the same choices; at most, a few might have beat the odds and ''not'' passed out when they dove into the water, but they'd just have surfaced a little faster and completed their cycles a tiny bit sooner.
*** Confirmed by WordOfGod [[http://www.radiotimes.com/news/2016-01-07/steven-moffat-has-filled-in-the-plot-holes-from-doctor-who-heaven-sent here]].
[[/folder]]

[[folder:Required time]]

* How long would it really take to punch through a wall ''20ft thick and 400x tougher than diamond''? Assuming the rate of the few punches he does, every 2 days...
** FridgeBrilliance: The wall wasn't actually Azbantium, but a manifestation of ''the Time Lock'' that keeps Gallifrey cut off from the universe. The Doctor's status as a Time Lord has previously allowed him to physically bull his way through Time-based obstacles, as per his ability to move with great effort when time was frozen in "Invasion of the Dinosaurs". In this case, that ability to ''force'' one's way through such barriers was exploited by the Confession Dial to ensure that '''only''' a legitimate Time Lord could break through, albeit in the cruelest way possible.
** Also, remember what the Half-Faced Man said in Deep Breath? The Doctor, like all Timelords, is stronger than he looks.
** Don't forget the effect that sheer time has on any substance. In two billion years even diamonds would turn into dust from nothing but contact with air. It's possible that the substance was growing increasingly brittle as the Doctor went along.
** His obstacle was a six-meter thick wall and he faced it about 300 billion times. This means that each time he had to wear out 20 picometers (20 * 10^-12) off the surface by average. Combined with his bounding box, that comes as about 0.018 cubic millimeters of the crystalline material, each iteration.
** Plus due to the gaining distance, progressive iterations would have more time to punch more.
** And probably more enthusiasm, as they'd be able to see clear evidence that he's going to make it eventually.
** The best guess of the Sisterhood is that the Doctor was inside the dial for 4.5 billion "years," as indicated by the simulated sky outside the simulated castle, and always remembering he has no memory of previous loops, starting each loop with the same body and the same memories. Assuming the Doctor reaches room 12 every two "days" of the simulated "years," that's 821,812,500,000,000 punching events. Call it about 822 trillion.

[[folder:Second of Eternity]]

* The king asked "How many seconds are there in eternity?", not "What is a second of eternity?". And whether you use those special seconds or just plain old seconds, shouldn't the answer to the king's question be the same? There are infinite seconds in eternity.
** The point to the shepherd boy's answer isn't to give an actual number: it's to express to the king that counting off seconds is irrelevant to the "eternity" concept. ''Any'' finite amount of time, whether an actual second or the eons it takes the bird to wear down the entire mountain, is inconceivably brief from the perspective of eternity.

[[folder:Portrait]]

* Did Clara's portrait show its actual age, despite the bedroom's reversions? The Doctor judges it to be "very old" when he examines it in the first iteration shown, and a later shot when he's moving from room to room gave a glimpse of a chamber with empty picture frames on its walls. If so, did his later iterations only see an empty frame and a pile of disintegrated canvas dust which isn't a bad reminder of her absence in itself...?
** An earlier Doctor may have painted it.
*** The fact the Doctor painted the portrait was confirmed by Steven Moffat in an interview published in ''Doctor Who Magazine'' #495.

[[folder:Confession dial workings]]

* So the Doctor was teleported into the Confession Dial. He told Ashildr in "Face the Raven" that he didn't know how it worked, and it was said earlier in the season that it could only open when he died. What was the point of the castle if the dial didn't actually contain the Doctor's confession? Why would it have contained a fragment of the Time Lock capable of being destroyed by the Doctor and the Doctor alone? Why would the Doctor have given the dial to Missy, if she couldn't have used it to get to Gallifrey (and it didn't have his confession ready to be played)? How did the dial itself get to Gallifrey from Ashildr (since we see it open to let the Doctor out at the end of the episode)?
** Possibly the dials are normally used to create a captive copy of a Time Lord's personality, whose intellect can be transferred into the Gallifreyan Matrix upon their final death. Each dial would need a communication-link to Gallifrey to do this, and the true nature of the dials would be kept secret from all but the highest-ranking Time Lords to ensure that link couldn't be exploited to hack the Matrix. When Gallifrey became Time Locked and trapped in its pocket universe, the link to the Doctor's dial got blocked by the crystalline wall, so instead of having to work his way into Room 12 just once, the Doctor had to ''punch'' his way in. The castle, Veil, and mechanisms were all custom-generated to drive him into Room 12 and goad him into entering; the fact it took him several billion tries was an unintended consequence of the blockage being there. By the time he managed it, his confession dial had been brought into Gallifrey in the same way that the white-point star diamond got ''out'' of the Time Lock for "The End Of Time", and had been adjusted so that it'd construct yet another copy of the Doctor's body for him to occupy there as he stepped through the link, instead of dumping his disembodied mind into the Matrix. Alternately, there are actually ''two'' copies of every confession dial: one to be carried by the Time Lord it belongs to, and another left safely behind on Gallifrey, both of them linked to the same BiggerOnTheInside pocket reality. As for why the dial requires confessions, it's to prime the deceased Time Lord personalities to give up all their secrets to the Matrix: something they'd otherwise be reluctant to do.
** The answer from "Hell Bent": the Confession Dial is designed to give dying Time Lords a chance to live peacefully and get whatever they need to off their chests before they're uploaded to the Matrix. The Doctor is rather angry that it was used to torture him into giving up information. Gallifrey escaped the Time Lock/pocket Universe on their own at some point offscreen, and the Dial was brought there so Rassilon could hear his confessions.

[[folder:Killed by the Veil]]

* When the doctor is killed by the veil, why doesn't he regenerate?
** Is there any actual death involved? Or is the castle, the veil & the transporter a tailored, repeating format the dial uses to elicit confessions. If so, is that how the dial usually works or are the Time Lord council using it to find the Hybrid?
** Time Lords are capable of stopping themselves from regenerating, like the Master did in "Last Of The Time Lords". Given the Doctors plan required him to return to the transporter room and create a new copy using his life energy it's likely that he stopped his regeneration on purpose.
** Except if he ''could'' still regenerate, doing so would have been the logical course of action: he'd have had plenty of time to come up with a better way to break through the wall than punching it, because the Veil'd disappeared after it grappled and wounded him. Instead, he muses about how Time Lords take a long time to die even when wounded too severely for regeneration, suggesting that's the state he's in.
** Did you miss the entire speech that he gave at the end? There are some deaths that even regeneration cannot cure. The body tried but it simply could not.

[[folder:Location of the dial and the teleport]]

* When the doctor transported at the end of "Face the Raven", was he sent into the dial which was itself sent to Gallifrey or was the Doctor sent direct to Gallifrey and his confessions given at some other point (the recording being in existence since "The Magician's Apprentice")?
** The bracelet probably transmitted him into the dial. He did say that the maximum range for a long-range teleporter was about a light-year, and Gallifrey was a whole lot farther off than that, even ''before'' it got dumped into another dimension.
** That bracelet is probably very similar to the one Missy used in series eight.

[[folder:The Doctor making the Confession Dial]]

* Let me see if I've got this right: The Doctor made the Confession Dial, then someone or something made a deal with Ashildr to trap The Doctor inside his own Confession Dial, and then The Doctor broke through it into Gallifrey. Who's plan was this? Did The Doctor set up this insanely elaborate plan and then erase his memory in order for it to work? If he knew how to get to Gallifrey in the first place, why set any of this up? Or was this some plan somehow set in place by The Timelords from within the Time Locked Gallifrey?
** The Doctor notes to Ashildr that he has no idea how a Confession Dial ''actually works'', implying that he didn't build his own. Keep in mind, the Time Lords sent a message back in time into a child's head to get out of the Time Lock on the War, Rassilon sent the Master a White-Point Star from within the Time Lock, and they were able to send regeneration energy through The Crack on Trenzalore - in short, they're locked up, but not powerless. The functions of the Dial may very well have been engineered by them at any point before (or after, since they're big on closed-loop paradoxes) their return to get them out of the lock, and sent back in time to the day he picked it up.
** Indeed, so far as the Time Lords know, the Doctor's the only one left who might still ''want'' to bring them back, now that the Master/Missy knows how they'd been exploiting her since childhood. They're hoping he can manage it before the silly sod gets himself killed, but can't count on that given how dangerous his life is. It's very likely that they rigged his Confession Dial to ensure that if he died, he'd be downloaded into it Nethersphere-style and have one last posthumous chance to penetrate the Time Lock. Then they lucked out, and managed to manipulate Ashildr into transporting him into the thing while still alive, same as Missy could visit the Promised Land via her own bracelet.

[[folder:Grave confession]]

* What was the Doctor's confession at the bottom of the grave? He realized that the Veil wouldn't kill him if he confessed, and stated "it was a lie, it was always a lie"; everything he said before that was too quick and... Scottish... to comprehend.
** He said he hadn't left Gallifrey because he was bored, he left because he was ''scared''.

[[folder:The Veil as a threat]]

* So, was the confession aspect of the trap just an ExcusePlot or did the creator of the whole scenario actually expect to get to know something about The Hybrid as a result of it? The Veil actually does very effectively kill The Doctor on contact, so it's a genuine threat - but it's actually too much of a threat to be useful as a torture mechanism (since The Doctor only has to resist once before, well, dying). The general theorisation here is that The Point was to get The Doctor to break through to Gallifrey, but this seems like a needlessly complicated way to do that, as well (why have The Veil be this deadly if you want The Doctor to act most effectively to get through that wall). This feels more like it's actually intended as an existential punishment device, rather than an effective means at either of the two previous ideas...
** Which also leads to the thought - who hates The Doctor enough to do this to him? The Doctor has previously mentioned that nobody hates him as much as he hates himself...
** Or someone wanted him to be very pissed off when he finally got to Gallifrey.
** Or someone just plain didn't have any ''other'' way to get him there, and needed him to do so no matter how much it hurt or angered him.
** "Hell Bent" provides the answer: Rassilon wanted to know what the Doctor knew about the Hybrid, and didn't actually anticipate him spending four and a half billion simulated years chipping away at a diamond wall with his fists.

[[folder:Spilling the secret at the end]]
* So, the Doctor is so determined not to reveal the truth about the Hybrid that he endures two ''billion'' [[note]]thousand million for those using the long scale...it seems implausible that they'd jump from hundreds of millions to millions of millions quite that suddenly[[/note]] years of repeated torture and death....and as soon as he escapes the trap meant to force the truth out of him, he just spills the beans for no apparent reason?
** They just spent billions of years scaring him to death. Now that he knows it's the Time Lords who were behind it, why wouldn't he want to return the favor?
** Because all the reasons why that secret could never be told should still apply just as much at that moment as it did one minute earlier when he was punching the wall.
** He couldn't tell them then because he wasn't ''on Gallifrey'' yet. If he'd admitted it while he was still trapped in the castle, they could've dumped his Confession Dial in the nearest trash-disintegrator and checked "Avert the Hybrid menace" off their To-Do list. Now it's too late: he's arrived, and their plan to identify the Hybrid has only succeeding in ''bringing'' him there, implying the prophecy is fated to play out despite their best efforts to stop it. And they'll '''know''' that.
** He may be lying through his teeth. There were *two* Time Lords of questionable provenance connected up to the Cloister Room during the [=McGann=] film, and the only other evidence of the Doctor being half human comes from the Doctor's own lips (pathological liar) and something shown to the Master by the TARDIS - who would probably quite cheerfully lie to the Master as well. Russell T Davies- admittedly, no longer in the driver's seat- has always maintained that a) the [=McGann=] film is canon, and b) the Doctor is ''not'' half human. Perhaps the closing line is not so much a confession as it is "Right, now to scare the Time Lords silly by telling them the Hybrid is coming for them, to keep them off the scent while I try to figure out what the hell to do about the *real* Hybrid...
** He is doing it for dramatic effect, to convince any eavesdroppers that he really does know. But he slips the sonic sunglasses on just before speaking the last two words. Maybe he's deliberately using the sunglasses to generate some kind of interference field so the eavesdroppers can't hear the last part of what he says.

[[folder:Repeating the loop]]
* In the billions of years that the Doctor is there does he do anything slightly different each time he is there like turning left instead of right?
** Possibly the first few iterations didn't get far enough to reach Room 12, and had to crawl back to the entry chamber without ever seeing the crystal wall. But as soon as one of him happened to win through, the others to follow would do exactly the same thing each time, because his previous selves had left the necessary help (BIRD, dry clothes) for him to solve the puzzle. From that point, all his iterations' lives were pretty much the same, because they all have the same mind and make the same choices; at most, a few might have beat the odds and ''not'' passed out when they dove into the water, but they'd just have surfaced a little faster and completed their cycles a tiny bit sooner.
*** Confirmed by WordOfGod [[http://www.radiotimes.com/news/2016-01-07/steven-moffat-has-filled-in-the-plot-holes-from-doctor-who-heaven-sent here]].

** But clearly the teleport room is exempt of the reset, or the reset doesn't happen immediately after he dies, since the word BIRD remains there when he rematerializes. So why not leaves the shades in that room for the next incarnation to find?

* So billions of years pass and not only do the Time Lords never think to just free the poor, mad Doctor from his SelfInflictedHell and instead just let him get madder and madder, '''nobody in the universe cares that the greatest hero space and time have ever known, is missing?''' It's possible that all his friends, colleagues, loved ones, etc. across the eons just don't realize he's trapped and suffering since he ''is'' a constant wanderer, but still...you'd think Rigsy or Anahson and her mum would have raised the alarm with UNIT that he was effectively kidnapped, or UNIT might have noticed his TARDIS is abandoned and companion dead...

* So billions of years pass and not only do the Time Lords never think to just free the poor, mad Doctor from his SelfInflictedHell and instead just let him get madder and madder, '''nobody in the universe cares that the greatest hero space and time have ever known, is missing?''' It's possible that all his friends, colleagues, loved ones, etc. across the eons just don't realize he's trapped and suffering, since he ''is'' a constant wanderer, but still...you'd think Rigsy or Anahson and her mum would have raised the alarm with UNIT that he was effectively kidnapped, or UNIT might have noticed his TARDIS is abandoned and companion dead...

* Since the Doctor's sonic shades are with him, why doesn't he do anything with them to break out of the loop faster? While he crawls to the teleport room, he could record a detailed message describing the nature of the castle to his future self into the glasses memory. Then, instead of leaving the cryptic ''BIRD'' message behind, a message whose meaning he only figures out when he's already in Room 12, he could leave the ''shades'' behind for his future iteration to found. At the very least, he could record the message, ''bring the spade with you to Room 12!'', into the shades, thus making the process of digging through Room 12's wall faster. That's the least he could do, but given the Doctor's skills, it shouldn't be impossible to re-engineer the glasses into some kind of laser or force beam device, which would make the process even shorter.

* Since the Doctor's sonic shades are with him, why doesn't he do anything with them to break out of the loop faster? While he crawls to the teleport room, he could record a detailed message describing the nature of the castle to his future self into the glasses memory. Then, instead of leaving the cryptic ''BIRD'' message behind, a message whose meaning he only figures out when he's already in Room 12, he could leave the ''shades'' behind for his future iteration to found. At the very least, he could record the message ''Bring the spade with you to Room 12!'' into the shades, thus making the process of digging through Room 12's wall faster. That's the least he could do, but given the Doctor's skills, it shouldn't be impossible to re-engineer the glasses into some kind of laser or force beam device, which would make the process even shorter.

* Since the Doctor's sonic shades are with him, why doesn't he do anything with them to break out of the loop faster? While he crawls to the teleport room, he could record a detailed message describing the nature of the castle to his future self into the glasses memory. Then, instead of leaving the cryptic "BIRD" message behind, a message whose meaning he only figures out when he's already in Room 12, he could leave the ''shades'' behind for his future iteration to found. At the very least, he could record the message "bring the spade with you to Room 12" into the shades, thus making the process of digging through Room 12's wall faster. That's the least he could do, but given the Doctor's skills, it shouldn't be impossible to re-engineer the glasses into some kind of laser or force beam device, which would make the process even shorter.

** It wouldn't be too much to think that, after a decade of debate over the Doctor's real age, and the script for "Day of the Doctor" indicating that he doesn't really remember his true age anymore, that this could act as the mic drop on how old the Doctor is. Once you get into the billions, age becomes meaningless. Physically, however, the Doctor is only a few days/weeks older than he was when Clara died on trap street.