A History of the Forbidden Land
There are several elements in Shadow which link it to Ico. Light Magic, Dark Magic, Dormin's appearance and Wander's possessed appearance, the infant at the end, and the general theme of living beyond your natural lifespan. Few of these can actually tell us anything though, most are just isolated pieces of the larger puzzle. Here I have collected some of the smaller pieces which don't directly connect to any others.
The Fortress and the Forbidden Land
The Fortress in Ico and the Forbidden Land in Shadow were obviously built by the same race. The architecture varies between similar and identical, and Light Magic plays a significant role in both. One interesting difference is that while the Forbidden Land is in ruins, the Fortress is still in pretty good condition. This is most likely explained by the Queen's influence; while she is alive the Fortress is mostly intact, but as soon as she dies it is completely destroyed. It is probable that, despite initial appearances, these two places are roughly the same age.
Yorda & Wander's Fates
At the end of Ico Yorda remains behind in the collapsing Fortress in her dark form. Through unknown means she later turns up on the beach near Ico, back in her original form. No explanation is offered, and it can only be assumed to be the same kind of convenient occurrence which saved Ico more than once. However, in Shadow we see something quite similar; Wander is taken over by Dormin and becomes a Dark Being. When Dormin is later destroyed, Wander is returned to something like his original form, again somewhat inexplicably. In both cases someone becomes a Dark Being and then returns in their original form after the Dark Being is destroyed.
As discussed, the Forbidden Land and the Fortress appear to have been built by the same race, the race which I label the 'Ancients' in my Ico analysis due to them having been around long ago. That each was built by the same race does not necessarily mean they had any significant connection to each other, simply that they were closely related enough that these two different places ended up looking very much like each other.
In Ico we are left with the question of where the Ancients went when the Fortress was abandoned. There is no trace of the Light Beings, other than the Queen and Yorda of course, but there is one possibility on offer regarding the humans. I suggested that Ico's village may in fact be made up of descendants of the human population of the Fortress. Shadow suggests exactly this kind of scenario even more strongly. As I mentioned in both Resurrection and the character analysis, Wander's people, and Emon in particular, represent the people who sealed Dormin in the 'present day'. They have the sword, know the legends, and share the desire to see Dormin sealed, with the obvious exception of Wander who has an agenda of his own. It seems highly likely that these people are indeed descended from the Ancients who inhabited the Forbidden Land. In Shadow's case there is no reference of any kind to Light Beings, we would not know such people existed were it not for Ico, so while it is likely there were such people in the Forbidden Land, we know nothing of them or what became of them. However, the idea that there was a second group of people, who were more closely tied to the magic, who then disappeared while the humans lived on, may explain the more mystical view of Light Magic that Wander's people seem to take.
While Emon is apparently knowledgeable about what is going on, he nonetheless seems to have no power of his own, and must rely on the sword to seal Dormin, just as Wander has to use it to free it. This is very much like the role of the sword in Ico, which provides a way for humans to activate the Light Magic devices such as the Idol Doors. If the Forbidden Land was indeed inhabited by both Light Beings and humans, no doubt the former would have been responsible for all of the instances of Light Magic seen there. With the masters of that power gone, the humans would of course have trouble making use of it, having to rely on relics like the sword. Having a more restricted use of it for a long enough time may have caused them to assign it an undue mystical aspect. When we see Yorda use Light Magic, she uses it in quite mundane ways, to open doors and similar which respond to the power. However, if our only knowledge of Light Magic was a sword which had been passed down through generations and supposedly held power over the seal on a supernatural being who can raise the dead, your impression of Light Magic would of course diverge from the more practical view presented in Ico. Thus what may have been little more than an energy barrier to the Ancients ends up being seen as a mystical spell by their descendants.
Written by Crumplecorn