If I may I'd like to briefly detour from my usual pure geekiness to explore some of the moral, and religious complications and issues raised by the game, and in particular the high ground it claims by this mysterious "templar's treasure" that it introduces in the latter phases of the game.
I've made vague mention of this already, but I feel I should probably clarify that I'm a Christian. Now Christian means a lot of things these days, and terms I would use, such as "born-again" or "evangelical" to describe myself are sometimes aquainted with "nut job" today (though they are good terms to use) so I will try to briefly explain my position.
I believe that God exists first of all and that there is enough evidence from the bible, from nature and my personal experience for me to be confident in saying that. I believe that He has described Himself in the Bible and that it is a trustworthy account when it says he is good, loving, creator of the universe, judge, eternal, holy and the saviour of mankind. I believe that in sending Jesus (who is fully God) to die on the cross is the only way I can call myself a Christian and it is only because of His great love, which I in no way deserve, that I have hope and a future.
I've no doubt been vague or unclear here, but I thought it important to give some idea of my worldview - if you want to know more drop a comment, otherwise I'll get back to the game.
Ok, my research on the Crusades is somewhat cursory, but it needs be be addressed nonetheless, I will first deal with the crusades in general, then move of the the game's portrayal. The Crusades can be depicted as a war against Islam by Christianity - I beg to differ. The wars were made by political forces, such as the British Crown and the Papacy to expand territory and power and inspired by as well as using religious fervour to promote the cause. The wars began when the Byzantine Empire called for help against attacking Turks - The Pope got in on the game and called for all Christians to invade Turkish lands, promising immediate forgivness for sins if they died in battle (this is something a Christian already has through Jesus Christ and so it was a disgusting and putrid thing to offer to the poor followers who went out and got massacred) and the Dutch Kingdom set out and were soon followed by others. These wars expanded and went on for centuries, incorporating all sorts of political rivalries and factions along the way, which is where the game takes it's focus.
The game picks up in the time of the Third Crusade, about a century into the fighting, where the battle is fought between two legendary leaders: Richard the Lionheart, of England and Saladin of the Saracen forces. With Saladin succesfully retaking key locations and being surprisingly chivalrous to those defeated the time was very much one of confusion, perfect for creatures such as the Assassins and Templars to operate. The game makes a very fair portrayal of the times, with neither side as the monsters, but with most people simply seeking to get on with life and the darker figures on both sides being rooted out by the Assassins. The game also accuratly portrays the fact that individual leaders were often the cause of darkness in the lands. With the protagonist being a Muslim, the game does slightly favour the Islamic forces, but with their lands being invaded I guess it's kinda fair, but it doesn't take a chance for a cheap shot at Christianity or to pander to contemporary pro-Islamic media either.
So with this fairly well-balanced presentation (though I guess it might be more honest to present more of the horrors commited by both sides) I wonder why they chucked in what happens next.
A piece of Eden
The game deviates from plausibility somewhat by introducing the supernatural Piece of Eden, treasured by the Templars and Assassins alike. I felt this was a let down as it stretched the game beyond believable limits. I was happy with the futuristic gimmickry of the Animus, but an ancient superpowered object detracted from the magnificent middle-ages gameplay that makes Creed so great.
The object is recaptured by the Assassins early on in the game and left in mystery till the end. It is given the name "Piece of Eden" and attributed to it are such events as the parting of the Red Sea, the success of the Trojan Horse and "let a simple carpenter turn water into wine." It is revealed as a powerful illusion caster, but it's greater power is in the obvious debunking of all religion, the true goal of both Assassins and Templars, though they have different motivations and means.
I felt this was an anti-climactic and somewhat arrogant end to a game that had dealt so well with one of the most complex subject matters available. To have a weird orb that just disproves both Christianity and Islam as mere illusion is far to simplistic as well as a bit offensive as well as just plain boring. I admire it's guts in not just saying all religions are ok and all that PC garbage, but "all religions are lies" isn't a tremendous amount better.
The Crusades are an immensly difficult subject, and so many attrocities were commited in the name of Christ and through the political power of "The Church" that I expected a comelling and distrubing tale to be unravelled, but instead I got a piece of (alien?) technology seemingly thrown in just for the sake of it, and the game could have managed just fine without it - though sequels may redeem it's use somehow.
I'm rapidly running out of things to say so I'll end by saying that Assassins Creed had a great opportunity to deal with some very heavy issues through the video game media, but it seems to me that they wussed out of the big stuff and decided to smooth over it all with a nice simple "we know it all" answer - and that, for me, was a let down.
I'll just quickly reiterate that I am by no means an expert on the game or it's subject matter and if you think I'm in error please discuss and I'll endeavour to look more closely