A History of the Fortress
The Queen's Plan
Having examined the magic in Ico, and come to an understanding of the most likely way it works, we can now apply this knowledge to the events of the story to attempt to explain exactly what was going on. Of course, even with all the analysis so far, the story is still quite uncertain and open to interpretation, so even if you accept my analysis thus far basically as fact this version of events is still just speculation using those 'facts'. It does seem quite a likely explanation given what the analysis has told us however.
At some point in the distant past the Fortress was inhabited by the living. Who exactly these people were is unknown and for now irrelevant, I will discuss it elsewhere. Since we have decided that the Queen used to be a Light Being, and given her title as 'Queen', we can surmise that at this point in time she was still alive and ruled over the Fortress. The Fortress, and by inference its inhabitants, appear to have been opposed to Dark Magic, but the Queen's desire to cheat death, which is seen in Ico, meant that she used Dark Magic to keep herself alive.
Once the Fortress had been abandoned, time passed. Since the Fortress is so old by Ico's time that only the Queen's own power seems to be keeping it intact, it stands to reason that quite a lot of time passed. It is impossible to figure out what the Queen was doing with her time all those years, other than surviving. There are signs that there were people in the Fortress since it had started to fall apart, such as chains fixed to the ground where there used to be staircases, etc. These may be signs of events which transpired during this time.
At some point the Queen's body started to approach its limit and she decided to do something about it. Once again she would use the Casket Chamber to renew her life, but this time there was a complication. There were still people being born with horns in this time period, but far fewer. To facilitate her future use of the Casket Chamber, The Queen arranges to have them brought to the Fortress and sacrificed in the caskets when they reach a certain age. The villagers are willing to do this as they associate the horned children with a curse. Whether this is an actual curse inflicted by the Queen, or merely them blaming natural events on the children due to the threat of a curse is unknown, and doesn't really matter. Either way, the children are sacrificed, as the Queen waits.
This carries on for generations, until finally we catch up to the time period of Ico, and the final sacrifice approaches. The Queen has another step in her plan to carry out - the creation of a daughter. It is probably relatively shortly before Ico's arrival that the Queen creates Yorda - it seems unlikely that she has the appearance of a child for any reason other than that she actually is a child. Why does the Queen need this new vessel? Judging by the differences between the Queen's own appearance and Yorda's appearance after becoming a Spirit, the Queen intends something slightly different this time. The first time the Queen merely extended her lifespan, leaving herself mortal, if long lived, and still somewhat human looking. However, Yorda will become a pure Dark Being because rather than having her life extended, she will be killed and then resurrected, likely rendering her immortal. The Queen cannot extend the life of her body any longer, and certainly won't allow it to die even to be resurrected, so she needs a new body which will die in her place. This is Yorda. And, being no more than a future vessel for her mother, Yorda's desire to leave the Fortress is answered by imprisonment in a cage.
But a problem arises. Shortly after the final sacrifice is delivered, he escapes, and what is more, he frees Yorda. Ico's escape does not seem to be a problem for the Queen in itself - she will later offer him the chance to leave, and the Casket Chamber will operate despite being short one sacrifice. That he takes Yorda with him is a problem however, as the Queen sends the Spirits after her. The Queen does not get involved directly until Ico and Yorda have nearly escaped. Her first and last move against Yorda is to kill her, the penultimate step in the preparation of her new vessel. It seems that the Queen was unable to attack Yorda directly for the duration of her and Ico's adventure, as it is only when Yorda is weakened that the Queen finally makes her move. Yorda uses her powers to open the Main Gate, which takes a large toll, and on top of this the Orbs strike her down as they reach the halfway point of the bridge. The bridge starts to retract with Ico and Yorda on opposite sides. Ico tries to jump back, and almost makes it, but the Queen intervenes. Yorda meets her end as Ico falls into the ocean below.
Or so it seems. Ico regains consciousness on the cages hanging underneath the bridge. The cages are below an overhang, so he could not possibly have fallen on to them, and if he had the landing would have killed him anyway. But it happened nonetheless, because that is the kind of story Ico is. That something which is basically impossible can happen becomes important later on.
The Casket Chamber chooses this moment to bring Yorda back as a Spirit. It is likely the Queen was controlling it, and without her guiding hand it automatically activates. Since the Queen is not alive to take over the resurrected Spirit, Yorda is still herself, though in mind only. The disappearance of the Queen's influence also means that the Fortress is now finally free to sink into the ocean. Yorda goes up into the throne room and finds Ico unconscious. Realising what has happened and what is happening around her, she takes him down to the dock and sends him off in a boat by himself. It can't be said for certain whether she chose to stay behind or was unable to leave for some reason. The boat floats free of the Fortress as it disappears into the waves.
After the credits roll Ico wakes up in the boat on a sandy shore at the base of some cliffs. Walking down the beach he finds Yorda, who is alive and no longer a Spirit.
Ambiguities and Alternatives
Why did the Queen allow Ico and Yorda to run around for so long? The answer lies with Yorda - if Yorda is captured by the Spirits during the course of the game, the Queen immediately attacks and kills Yorda. It is Yorda's presence which prevents the attack - at least up until the incident on the bridge. The idea that the Queen was unable to attack is based on the fact that Yorda is a Light Being. As the Sword and the statues in the throne room demonstrate, Light Magic is able to block the Queen's attack. Since Yorda is a living source of Light Magic, not merely some magical object, it is possible that she was unconsciously blocking the Queen from attacking at all. Since the Queen has a frail physical form these magical attacks were probably her only direct option, so with Yorda removing that ability she had to rely on the Spirits. However, the effort of opening the Main Gate combined with the attack of the Orbs significantly weakens Yorda - and it is at this moment that the Queen turns up. It is probable that Yorda's ability to block the Queen's magic was reduced or removed at the point, and so the Queen took the opportunity to kill her. The weakness of this explanation is that while this assumed power of Yorda's makes perfect sense in the context of the magic, it is just that - an assumption. We cannot be sure.
Another question relating to the incident on the bridge is why the Orbs strike Yorda. One could assume the Queen's influence is responsible, that she used them to attack Yorda indirectly. However, the Queen being able to use a Light Magic device seems unlikely, since Light Magic negates her powers and eventually kills her. Furthermore, the Orbs activate just as Yorda crosses the midpoint of the bridge, and something also prompts the bridge to retract at that moment as well. If the Queen was in control, she could have used the Orbs against Yorda before she even opened the Main Gate. Rather, the attack of the Orbs seems tied to the fact that Yorda was about to leave - they did nothing until Yorda was a mere footstep from freedom, and did nothing to Ico. But just as Yorda was about to cross that threshold, she is stopped in her tracks and the proverbial door is closed. There is a sense of purpose about this, but what that purpose is remains a mystery.
Yorda's apparent choice to remain behind at the very end is another element which has no light shone on it. It is entirely possible that she chose because of what she had become. The Fortress, and by inference the people who built it, appear strongly anti Dark Magic. Yorda, despite being locked up, appears to know her way around the Fortress and its mechanisms, suggesting she knows a lot more than it appears. If she also understands what she has become, and views it in the same way as her people did, of course she would not want to live on in that form. In short, she has died, and does not share her mother's wish to live on as something else. The way she regards herself when she first wakes up in the Casket Chamber certainly lends credence to this idea.
I make the assumption that the Queen originally ruled over the Fortress simply because she is given the title of 'Queen' in the background material. It is possible though that this is simply a reference to the fact that she now rules the Fortress. It is therefore possible that she did not originally rule the Fortress, and may not have originally lived there at all, but instead went there to use the Casket Chamber to extend her life when her original body was nearing its end. She may have gone there before or after it was abandoned, and it is still possible in this case as it was in the case where she was originally the Queen that she is responsible for it having been abandoned.
Some contend that the scene after the credits is not a literal scene, but is actually Ico and Yorda being reunited in the afterlife, or merely a dream Ico has while in the boat, the 'evidence' being the fact that we cannot explain how Yorda ended up on the beach. Both of these points of view have numerous problems. Before I even address these problems I'll point out that lack of evidence does not necessarily mean there is an issue; we could easily come up with a plot reason for her appearance. For instance, perhaps the fact that the Queen didn't possess her body means that Yorda was always going to return to her old self, but did not realise it, and her dark form kept her alive long enough to float free of the Fortress? This is of course pure speculation, but only because we do not know enough about the magic involved. The point is that it is possible that if we understood Yorda and Dark Magic better that her appearance on the beach would be no mystery at all. However, since we do not possess the requisite understanding, I will examine the proposed alternatives nonetheless.
The idea that this scene is the afterlife does not work simply because Ico is injured. If this were actually the afterlife Ico would either have been healed, had his horns restored, or they would have been removed completely, since they are supposed to be a curse. It is definitely supposed to be the real world - so we move on to the idea that this is an illusion of the real world in Ico's head.
A first point against the dream idea is that there is a scene which we know is a dream near the beginning of the game, and it is presented in a way which makes it quite obvious that it is a dream. There is no suggestion that the scene after the credits is a dream, except that it is all rather convenient. Why make it quite obvious that the first is a dream, but then make second so subtle? But lets put that aside and look at the details.
Yorda's turning up on the beach is a surprise, and is hard to explain, but let's not throw away the entire epilogue of the story as a dream, or something equally unlikely, just because of one difficult to explain component. Instead, let's look at that one component. How can Yorda be on the beach? Rather than attempting in-universe explanations as I suggested above, my answer is that she cannot, but she is anyway. I pointed out in the main analysis that at one point Ico survives a fall which was impossible to have even happened, let alone to have survived, simply because this is the kind of story Ico is. The events of the story are meant to turn out a certain way, 'fated' if you like, and this requirement overrules the realism or likelihood of the story. Ico and Yorda and meant to survive and gain their freedom. This a fairytale with a happy ending. Many events from the coincidental freeing of the final sacrifice to Yorda turning up on the beach vary between unlikely and impossible. The scene after the credits is just a continuation of a natural pattern in the story.
And where is the pattern in the story which suggests they should not survive in the end? Nowhere to be found.
Written by Crumplecorn