Hi. I am a Spanish user and I would like to point some historical mistakes in the movie that, for me, had not very much sense. It is a very long post and it was a lot of work, but hopefully it will be useful for anyone willing to read. Sorry for my English in case something is wrong, as it's not my mother language and it is complicated to talk about historical things in proper terms in a language that it isn't your language.
I want to point first that it seems the Assassin brotherhood we see is really close to the Sultan of Granada, so I would say that we are shown the Granadian Assassin Brotherhood, instead of the Spanish Brotherhood, as Spain in that moment was actually divided in 3 kingdoms: Castile (Whose Queen was Isabel I), Aragon (together with Navarra, whose King of both was Fernando II) and The Emirate of Granada (Whose King was Muhammad XII). Castile and Aragon were both Catholic and united by marriage of their respective Queen and King (still 2 separated kingdoms, anyway), but Granada was mostly Muslim (With free of religion thought). I think this is important to note as traditions of this Brotherhood are closer to the ones we saw from Levantine Brotherhood, so I think it could be totally possible to have 2 or 3 different Brotherhoods operating in Spain in that moment, one for each kingdom, maybe collaborating between them as Italian Brotherhood could collaborate with the Turkish one. Actually when I played Discovery I always thought the brotherhood we see was actually the one from the kingdom of Aragon, as both cities Barcelona and Zaragoza, were in this kingdom, and that there wasn't a Brotherhood in Granada for some reason.
Ok, let's do this. First scene, first mistake. Year 1492. Ok, but... Granada surrendered January 2 of 1492, so the movie should start in January 1 and end January 2? I don't know...
Now, next scene in the past. Granada is sieged (we see the nowadays Spanish flag that wasn't used until almost 1800, moreover although as I said, there wasn't a Spanish kingdom yet). We see Aguilar and the assassins in Granada trying to avoid Prince Ahmed to get kidnapped. This is strange, as the one who was actually kidnapped was the Sultan Muhammad XII itself, but he was liberated in exchange of their 2 sons (Ahmed and Yusef) and his daughter Aixa. All of this happened at the beginning of the Granada War, in 1482, in the Battle of Lucena (a town near Granada). The children weren't liberated until 1492, ten years later, when the sovereignty of Granada was finally given to Queen Isabel I and King Fernando II (The Catholic Monarchs). The siege of Granada itself (that we can see in the movie) didn't happened until 1491 (9 years after the kidnapping).
Next scene in Aguilar memories, we see them as prisoners in Seville, where they are going to be executed in an Auto de Fe by the Inquisitor Torquemada. We see the King and the Queen are there, with their entire court, because... why not. I mean, Granada and Seville are relatively far in terms of distance for that era (nowadays you can take that distance in 2:30 hours by car, but by foot would take more or less 3 days, and the ENTIRE COURT of the King and the Queen used to move where they were, so easily we could be talking about more than a week of travel). I don't see a point on the Catholic Monarchs assisting to the Auto de Fé either, mostly because they were in Granada trying to win a war, but also because they didn't use to do it, as Inquisition was a separated thing from the crown. You could think they used to assist to the Autos de Fe because there is this painting in the movie that shows them with Torquemada. This painting, actually, is fake. It is a modified version of a famous painting called "Auto de Fe en la Plaza Mayor de Madrid" by painter Francisco Rizi. This painting shows an Auto de Fe in Madrid in 1680 (almost 200 years later), and there isn't bonfires and such, as bonfires were more related to the witch-hunt in other parts of Europe. The only way a prisoner could die by a bonfire would be for repeat offending (as they could be punished and not executed). Actually, this Autos de Fe wasn't public executions but trials. After the sentence by the inquisitor was made, if guilty, the prisoner was given to the executors that proceeded to make their job in a private place. The real painting shows Carlos II, the king in that moment. That was actually because the last one was celebrated in 1632 and it this one was celebrated in a very solemn way. Oh, and another thing. WHY. WHY Isabel I has her face tattooed all over lol. It is just ridiculous and has no sense at all as those kind of tattoos seem more close to Arabic traditions. Anyway, no painting or representation of her has those tattoos.
Next memory, they are again in Granada, where the Sultan is going to give the Apple in exchange of the Prince Ahmed. Here, something strange happens. After Muhammad gives the Apple to Torquemada, the fight begin and Muhammad and his son just... disappear. I don't know why, or how, but they just banish. This is not a historical mistake but I wanted to point it as I paid close attention in order to see if they run away or any of them die or what, and I was quite surprised that they are not shown again.
There is something else I wanted to discuss, although this is more an interpretation issue. As Torquemada is shown being really close to the Queen and the King, it is shown as if he had even more power than them. This is just untrue. Ok, of course Torquemada had a lot of influence but he wasn't as powerful as it's shown. In Assassin's Creed Discovery we are told there is an Assassin in the court, Luis de Santángel. Also, in Project Legacy, Isabel I is shown as a harm for the Assassin cause. As there are certain true shadows on her decisions, such as the expulsion from Spain of all Jews, I would consider her, personally, more close to the Assassin cause than the Templars one. Why? Because the religious decisions she made, such as the expulsion of the Jews, were actually motivated by the Pope Innocentius VIII and the Inquisition. At this moment, all Europe had already expelled Jews but Austria, Portugal and Spain. She actually tried to convert them to Christianity before expelling them and really tried to protect them as much as they were able. They also opposed to slavery in America, and that's why Spain mostly never practiced slavery in next eras. Furthermore, they jailed Cesare Borgia for 3 years until he was able to escape and went to Viana.
Hope this have been interesting for everyone who had the will to read it. Let me know what you think about everything.