I read this thread a year and a half ago and was unprepared to add anything to it without re-reading Heretics. I just finished my latest read-through last night and I think I can help a little.
For one thing I somewhat consider it a flaw in Heretics that most of its content cannot be fully deciphered without reference to Chapterhouse, and inasmuch as they may be true I can't comment on it since I'm only starting my re-read of CH:D tonight. I don't think the basic content of a book should require reading another book to understand it, but that's just my opinion. I almost feel that Heretics and Chapterhouse are basically a duology; almost one book split into two sections much like Dune was originally in three sections. Anyhow here's my go at the facts:
The real BT were the ones who attacked Gammu keep, but Schwangyu thought the HM were behind it. The likeliest reason for this conclusion is that - as we learn in the last chapter of the book - the local BT had already been corrupted by the HM and were under their control. Odrade mentions in passing (!) that she recognized that Waff's one encounter with an HM imprinter left him under her control despite his protestation to the contrary. The quote says it was merely one of his Face Dancers and not an HM, which might lead us to believe that even if he was imprinted it was by a loyal BT subject and therefore the control over him wouldn't actually benefit the HM (especially since he claims to have destroyed the FD that did it to him). However we also learn in the book that the NFD's lose their original sense of self and believe they are the adopted persona. This is shown to us in a detailed scene involving the fake Tuek. This might well mean that the 'fake' HM that imprinted him really thought she was a true HM and that she was controlling him for the HM agenda, and she may well have done just that. Maybe she was destroyed in the end, maybe not, but if not she could certainly coerce him to say she was while she went on imprinted other masters. distrans is right that this is barely
alluded to but is one of the most critical plot points.
Another question is whether Taraza always had the same plan in mind, or whether her plan was modified on the fly based on current events. I think the text suggests that her plan was never modified, and that it was to have Duncan and Sheeana lure in the HM to destroy Rakis, for the purposes of releasing the universe from the Tyrant's endless dream. This could only be safely done, however, if access to BT spice was guaranteed, which should lead us to conclude that the ability for the BT to produce spice was an extremely
recent development. I imagine that Taraza's plan was only devised after learning of the BT supply and testing it, which may mean that it was during Taraza's tenure as Mother Superior that the BT developed this capability. It would also explain why Taraza chose that time to hasten the destruction of Rakis; the BG were tethered to Rakis and because of that any force that wanted to hunt them down would only need return to the old Empire to find them. By removing Rakis from relevance the BG would be freed up to go anywhere at all and lose their dependence on it. Dependencies and key logs; the dependency was on Rakis and the way of life known to the Sisterhood for eons, and Teg was the key log to release them from that. The bit about the pearls of awareness was, I think, relevant, but it may have been more of a psychological trick played on the BG to make them think they were trapped into Leto's vision and needed to escape. The key idea here being - that they needed to make a big change, and the idea of the pearls of awareness was the trigger to make them think they had to make that change. Whether Leto's visions actually
were still having effect would seem to be moot, since as long as the Sisters thought
they were then, in effect, they were.
Now we get to Duncan. The Sisters wanted him to be trained to seduce Sheeana, and to therefore take over the Rakian priesthood. The big question is: why would the HM destroy Rakis just because of that? Why would they care if the priesthood was controlled by the Shai-hulud worshippers or by the BG? The Tleilaxu would certainly care, that's for sure. In fact, since Taraza's plan had been in effect for many years (enough for 12 Duncan gholas, as well as time enough to complete the search for someone like Sheeana), we assume she had taken into account these variables back then. Could the BG have known about the HM sexual techniques way back then? The BT certainly didn't, but maybe Taraza did. I'm not sure if the text would back up this possibility. Even so, the only thing that would offend the HM enough to destroy a planet would seem to be the ability to replicate their techniques or at least resist it, so let's say for argument's sake it was Duncan's sexual abilities that made them complete Taraza's plan. In that case the BG must have planned to teach Duncan how to be an imprinter after being imprinted himself by Lucilla. It seems like such a plan would, indeed, be offensive to many BG, since I think such powers and duties had previously been restricted only to the females. When we consider that a RM actually went rogue on account of this schism, it must have been over something very serious. Creating a male imprinter would probably be enough. It was also likely a calculated gamble that BG imprinting techniques present in a man would be enough to bring down the wrath of the HM on Rakis.
Now we get to the BT and Duncan, which was the OP question. By total coincidence, I guess, the BT had also been given the HM techniques by the BT from the Scattering, and they implanted this ability in Duncan, which removed the necessity for Lucilla to teach him those skills. Another big question is why Taraza ordered Teg to prevent Lucilla from imprinting Duncan. I think maybe it was just so Duncan could be awakened first and imprinted afterwards, since it seems that once he was awakened Teg ceased interfering with Lucilla. At that point it was Duncan himself who prevented her attempts, which was perhaps not according to plan. Since we know Teg was a latent prescient he may have had an instinct (like the sort Odrade sometimes had) that things were going to work out ok anyhow and not to force Duncan to submit to it. This was the first instance, I think, of him altering Taraza's plans on the fly.
It takes reading CH:D to know the other ability implanted in Duncan, but to my surprise that ability was actually hinted at here in Heretics. I never understood it before, but now that I do it's crystal clear and makes complete sense from the BT's perspective. They had already perfected serial-ghola memory, which was a kind of immortality. However this advantage could only go so far as each lifetime still had to be lived, so in terms of 'data collection' this process of a master acquiring knowledge would still be 'slow.' They had also perfected the ability to splice DNA from various beings to change the characteristics of another one; for instance they could take the original Duncan cells and add other material to them to create a modified Duncan. The implication of this should already be clear - when growing a new ghola, should not those spliced cells have memories of their own? It seems so far that only the 'majority' person regrown had his memories restored when awakened, but there were
cells or DNA from others present in him as well in small part. The next logical step in the BT plan would be to find a way to awaken the memories in those spliced cells as well so that they could regain not only the serial memories from the ghola's past life but the memories of the lives of those combined into the ghola. And once this technique would be available it would be possible to take any being whatsoever and add his DNA to that of a master and acquire of of his memories in the master's next serial life. The collection of memories! And here we have a quote from Heretics that took me aback because I hadn't remembered it:
Did they dare risk releasing Duncan from the shielding of that ship? The cell studies said he was a mixture of many Idaho gholas -- some descendant of Siona. But what of the taint from the original?
This was not an original Duncan, modified with enhanced abilities as the BG requested! It was a composite of "many" Duncans. How many? If I'm right that the next and perhaps final stage of the BT plan was to create a composite ghola of many beings and to awaken all of their memories, then Duncan was their prototype in this. I believe Duncan was a composite of ALL of the serial gholas through the Tyrant's time, or at least as many as could have their cells harvested before or after death (before death would still be good enough for these purposes). I expect that the BT would have been able to extract cells from the Duncans at some point or another so that the collection could conceivably have been complete. I also think that the BT plan for awakening the dormant serial personas was not part of the BT plan on Gammu, but was going to be realized later if their initial test on Gammu ever proved to be successful. The initial test being the test to see if he could reverse imprint and/or kill a BG imprinter. My guess is that the BT killed the previous Duncans right after the BG imprinter did her work on him and the BT sexual techniques failed. At that point they would scrap that Duncan and try again. But if he ever did succeed he would likely be able to come to control the BG on Gammu and the BT could then reclaim him for part 2 of the experiment to try to reactivate his dormant memories. Another thing we may notice is that Teg's awakening procedure did reawaken his original
(majority) DNA, that of Paul's Duncan. But it did not awaken the rest of the DNA, meaning that another more advanced secret step would be needed for that. This way a master could first regain his serial self and after that acquire the additional memories to add to his own. If it was all done at once the masters would face the same problem as a BG abomination, as the master's own persona would likely be lost in the morass and he would not be 'the same person' he was in the previous life.
Since the 12th Duncan was, in fact, a total success, the BT would have wanted to reclaim him rather than destroy him, and I think Freak's explanation for this is on point. By this time the HM's had infiltrated and taken control of at least some of the masters (including Waff), and they made
the BT attack the Gammu keep to destroy the ghola. This was a disruption to Taraza's timetable since the HM learned of Duncan's powers earlier than she intended them to (and before the BG had even taught them to him). So in short, my explanation is that the decision to destroy this ghola even though they had previously stated that the timing was carefully prepared and that this ghola was the one, is that the BT didn't make this decision at all and were probably very upset at being made to do this. This quote of Waff's is telling, but only in hindsight:
Waff flared: "She thought to . . . to hire us like a band of assassins! We only taught her a lesson!"
Ahhhh, his pride shows itself, Taraza thought. Interesting. The implications of a moral structure behind such pride must be explored.
Taraza sees pride here, but she mistakenly thinks it's the pride of having Waff's honor impugned by being asked to work as a mere assassin. I think his pride was already wounded because of being made to do something he didn't want to do by HM control, and his statement here is an excuse and a lie to cover the fact that he wasn't in control of himself any more.
I won't say any more about the desire for the BT to develop the ability to acquire memories, but let's just say this idea may have been given to them by the returned BT from the Scattering after seeing what the SFD's there could do. They may have been trying to warn the original BT on how to develop countermeasures to this by becoming acquirers of personas themselves as masters, rather than being overcome by the SFD's who could develop this capability first. The amazing thing in Heretics is that this detail is only in the background and yet it is the entire reason for the HM return to the old Empire and would become the likely focus of Dune 7.
And one more thing I noticed that confused me when I read it:
Taraza who had played such a dangerous game with the future of the entire Sisterhood hanging in the balance! How carefully she had timed the leaking of word to the whores that the Tleilaxu had built dangerous abilities into the ghola. And the attack on the Gammu Keep confirmed that the information had reached its source. The brutal nature of that attack, though, had warned Taraza that she had little time. The whores would be sure to assemble forces for the total destruction of Gammu -- just to kill that one ghola.
So much had depended on Teg.
Could this be a typo? I think Frank might have meant the total destruction of Rakis, since that is exactly what happened. There seems to be no evidence in the book that the total destruction of Gammu was going to happen, especially since the HM had such total control of its territory that finding all three fleeing parties (Teg, Lucilla/Murzmali, and Duncan) seemed quite simple for them.EDITED TO ADD
: I just realized something else huge. Why would the BT put both of their experimental projects in the same ghola? Why not test the imprinting ghola on the BG and test a composite-lives ghola somewhere else safe? The answer can only be one thing, which is that they didn't merely want to create the ability to collect memories, since memories from one being is nice but limited. What they really
wanted was to collect a BG set of memories (as M&D finally just say at the end of CH:D, but which is hinted at here) . That way, the BT would be able to splice the entire set of BG ancestral memories onto a BT master, and he would effectively be an even superior version of a RM. THAT is why the same Duncan ghola was given the reverse imprinting skill as well as the combined Duncan DNA - they wanted him to not only corrupt the BG who tried to imprint him, but also to take her or at least her cells back to the BT. It's also possible they thought the reverse imprinting activity itself would reawaken the combined serial memories, which actually it kind of does. Towards the end of Heretics there is a passage I can't find right now that even hints at him having recollection of dying to the Tyrant countless times. So it looks like the BT experiment worked on both counts. When seen in this light they really appear to be crafty. This plan was actually quite excellent, but they were simply outplayed by Teg.