Ambiguously Brown: Desmond has three distinct bloodlines of various ancestral origins, so his character model is ambiguous enough to have come from any of them.
In the first few games, Desmond could probably have passed for Caucasian as well; with his updated character model in the third game, though, it'd be unlikely anyone would guess that.
Ancient Conspiracy: Combined with Conspiracy Kitchen Sink. It seems that most politicians or people of any prominence for the last 3000 years were Templars, Assassins, or aligned with/supported by one of the two groups. The Templars have rewritten history to conceal this, with near total success.
Animal Motif: Eagles for the Assassins. Their symbol looks like a bird, Alta´r's cloak has a beak-like hood and slits at the back that resemble tailfeathers, eagles are seen circling View Points, and all of the main story Assassins have a special ability called Eagle Vision.
Alta´r and Ezio's names are both derived from the word for Eagle in Arabic and Greek respectively. Ditto for Haytham and Aveline, Arabic once again and German.
Connor is more strongly associated with wolves than eagles. This is especially emphasized in alternate timeline DLC, where he never becomes an Assassin. American bald eagle still appears in trailers and certain sequences.
Annoying Arrows: Arrows take off a small portion of the health bar of the player character Assassin, but are a One-Hit Kill for most enemies.
The Anti-Nihilist: The Assassin Brotherhood, with their maxim of "Nothing is true; everything is permitted". Rather than being a doctrine or command to do what you want, it is more of an observation - that the truth must be divined by one's self, with guidance and forethought of the potential results.
Alta´r Ibn-La'Ahad: ...laws arise not from divinity, but reason. I understand now that our creed does not commend us to be free - it commends us to be wise.
Ezio Auditore da Firenze: ...merely an observation of the nature of reality: To say that nothing is true is to realize that the foundations of society are fragile, and that we must be the shepherds of our own civilization. To say that everything is permitted is to understand that we are the architects of our actions, and that we must live with their consequences, whether glorious or tragic.
Applied Phlebotinum: The various Pieces of Eden and other First Civilization technology serves this purpose, with different effects for each of them.
Back from the Dead: Some uses of the Shroud of Eden caused this. Additionally, the Ankh was capable of healing the sick, and temporarily resurrecting the dead. It also acted as a recording device, storing the mannerisms of a living person and being able to return those mannerisms to a corpse.
Portal To The Past: Crystal Balls act as a limited version of this, allowing people who use them to communicate directly with members of the First Civilization through visions.
Psychic Link: The use of Crystal Skulls, with the user of one such skull being able to communicate instantaneously and telepathically with a user of another skull who is holding one as well from vast distances. The Shroud also has one with the people who use it.
Video Will: The Prophecy Disk and Memory Seals seem to have been a form of this, showing life from centuries past.
Arc Number: 9 (Alta´r kills nine men for Al Mualim, Ezio assassinates Savonarola's nine lieutenants during the Bonfire of the Vanities and Brotherhood and Revelations both have nine sequences) and 72 in Brotherhood (which is divisible by 9).
Arc Words: "Nothing is true. Everything is permitted."
As Long as There Is Evil: Well, the Templars do not think themselves "Evil," but as long as there is human weakness, there will be those who wish to exploit weakness and take power.
Desmond's hooded sweatshirt. Just picture it with the hood up. In fact, he even puts it up in III.
Alta´r, Ezio and Desmond all have a virtually identical scar on their lips. Ezio acquires his in the tutorial for the second game.
As You Know: After the first game, each new game opens with an As You Know narration of the events leading up to it. Particularly egregious at the beginning of Revelations, when Subject 16 is lecturing Desmond about the things he did in the past few games.
Audible Sharpness: The hidden blade has a very iconic "SCHWING!" sound that plays whenever you assassinate someone with it. By contrast, activating it when nobody is around just makes a slight clicking noise.
Badass Long Robe: Most Assassins in Alta´r and Ezio's eras wear this sort of attire.
Benevolent Architecture: Every structure that you need to climb has grab points conveniently located on it. Every rooftop path is loaded with platforms, protruding beams, and flagpoles. Every tall building has a haystack beneath it to perform a Leap of Faith into. The architecture is designed so precisely that it can only be traversed by someone with the free-running skills that the Assassins possess (never mind that a tall ladder would make most of the puzzle segments trivial). As with many other gameplay elements, this is implied to be an embellishment provided by the Animus to make "playing" the memories easier for the subject.
Bigger Bad: Juno, who is responsible for everything that happened in the games so that it would benefit herself at the end.
In every game, each faction wears clearly distinctive colors so you can tell them apart at a glance. This applies to their minimap icons as well, when it's relevant.
Eagle Vision paints allies, enemies and targets accordingly to make it easier to tell NPC's apart from a distance.
Combat Pragmatist: All Assassins are masters at dirty fighting. When they say, "Everything is permitted," they mean everything is permitted.
Completion Meter: A staple in the series for "additional memories", such as collectable flags in the first installment, and eagle feathers in the second.
Counter Attack: One of the highlights of the combat system is the elaborate and visually spectacular counters, to the point of having a different set of animations for each weapon type. In fact, counters are the only effective way to fight multiple opponents in Open Combat up until Brotherhood introduces kill streaks and combo kills, making it practical to go on the offensive for the first time in the series.
Cutscene Power to the Max: Averted, at least in terms of the pre-rendered CGI trailers. Despite not being gameplay footage, almost every action they show can actually be performed in the game itself.
Cycle of Revenge: Some version of the Assassins and the Templars have been fighting since the First Disaster in repeated conflicts over Pieces of Eden, and Desmond and William both think in Assassins Creed III that the conflict will continue long after they die.
Dashed Plot Line: Most of the game takes place in "memory sequences", which are segments of memory in which significant events happened in the life of the main character. Individual sequences may take place over significant lengths of time and there are often lengthy jumps between sequences.
Equipment Based Progression: The games generally follow this format, in that you get better weapons to do more damage, and better armor to get more health (the first has a "sync" bar that increases through the game as you did various sidequests).
Existentialism: "Nothing is true. Everything is permitted." The answer to an existential crisis: If no gods exist, if there is no grand design; all that remains is what you choose.
Eye Scream: Some of the bladed weapon counter kills go for the eyes.
Fascist, but Inefficient: Whenever the Templars take full control of an area, they tend to run it into the ground due to their "keep the people weak" policy weakening the nation as a whole. So much for their Utopia.
The Fettered/The Unfettered: The Assassins strive for Freedom/Chaos, yet live by a strict moral code that defines all their actions. The Templars, in contrast, seek Order/Law, yet have absolutely no moral restrictions on their behavior and are free to use any and all means (up to and including mass murder) in pursuit of their goal. This leads to quite a few ironies, see Murder Is the Best Solution below. Ultimately, both the Assassins and Templars believe that "Nothing is true, everything is permitted". But to the Assassins the phrase is descriptive whereas to the Templars it's proscriptive.
Fling A Light Into The Future: The grand design of The Ones Who Came Before, who found themselves dying from underpopulation after a great catastrophe, was to seed the Earth with their artifacts and use their knowledge of the future to manipulate events so that key people would have the necessary information to prevent the same catastrophe from happening again. Alta´r's story in Revelations is an explicitly demonstrated subplot of this larger design.
Alta´r: They are... messages, of a sort. Niccolo Polo: Messages? For whom? Alta´r: I wish I knew.
Foregone Conclusion: Both the Assassins and the Templars make it to the 21st century intact, and the ancestor character survives to have a kid.
The Guards Must Be Crazy: The often incredible stupidity of the guards is justified In-Universe by the Animus not rendering memories precisely as they occurred, but rather as a VR simulation that Desmond must attempt to "play" as close to the way it really happened as possible. The assumption is that the real Assassins were much better at being inconspicuous than the player appears to be. There are also a few aversions in the second game onward, when the guards will act with surprising alertness and care, in particular by searching likely hiding spots.
Half-Human Hybrid: The "Truth" segments and the backstory exposition across the various games reveal that Alta´r and Ezio's bloodlines are descended from "Adam and Eve", who were real people that were part of an experiment in cross-breeding humans with the Precursors. They proved to be immune to the Mind Control effects of the Pieces of Eden and stole the original Apple, giving rise to the myth of Eden. They led a revolt against their masters and eventually gave rise to the Assassin order... and the Templars, through their son Cain.
Highly Visible Ninja: Despite a profession that requires stealth and anonymity, the Assassins wear an extremely recognizable uniform. It is more excusable in the first game when the white robe and hood lets them pass for Muslim scholars. In the Ezio trilogy... not so much. Not only do they all wear the distinctive robes and hood with the signature "beak," which stand out starkly against other Renaissance Italian clothing, but Ezio prominently displays the symbol of the Assassin order on his armor.
Ezio has an outfit that has an Order belt buckle almost as large as his head. No one ever suspects the guy wearing this outfit and bristling with weapons as the likely culprit of a mass murder, even when he is standing right there watching them in a crowd. It has to be noted that no one in the crowd is wearing clothes remotely resembling Ezio's.
High Speed Hijack: Starting with Brotherhood the games allow Horse-jacking, either when you're leaping from above or from a horse of your own. Cart-jacking is done too, in a few sequences.
For starters, the Hashshashin themselves. According to history, they were Hassan-I-Sabah's private army, and brainwashed with drugs to boot. They built a reputation at the time as his enemies were Asshole Victims whom they eliminated with a minimum of collateral damage.
There's no actual evidence that the Hashshashin were ever brainwashed with drugs at all. All evidence claiming this were written by the enemies of the Assassins, in order to discredit them. Hassan-I-Sabah killed his eldest son because He disobeyed his orders not to consume alcohol and hashish. Hassan-I-Sabah managed to get people to follow him, because He had the two things that make men and women follow their leaders into hell: Charisma and Conviction. Hassan-I-Sabah had earned and established a reputation among the Fatimid Caliphate in Egypt and the Seljuk Turks, for being a powerful orator who was firm in his beliefs and ideas. It earned him a powerful following. It was because of this, that the leaders of the Fatimid Caliphate had him exiled to Persia. His followers went with him into the Alborz Mountains, where Alamut is located at. Once there, He was able to fortify Alamut Castle and bring the surrounding towns and villages out of poverty. The name Hashshashin is a corruption of Assassiyoon, which means Followers of Asas', which is the core foundations of Islam, and not what different sects have interpreted them as. The historical Assassins had earned a reputation among the common folk for not only minimizing collateral damage and not going after them, but generally looking out for their welfare. To boot, they were actually allies with the historical Knights Templar, as their ideals and goals were very similar and close to one another. And to top it off, Alamut, the original HQ for the Assassins, along with their other castles such as Masyaf, Al-Khaf and Lamfsar, were renown for their libraries, which was open to scholars and pilgrims, who wanted to come and study from them.
King Richard I of England gets a fairly realistic representation: he went by the title "Lionhearted" even in his own day, and it did not refer to heroism but a love of combat. So, though he's driven to conquer Jerusalem, he keeps his promise to listen to Alta´r after he beats Robert De Sable in single combat, and lets Alta´r go free afterwards. He's undeniably a jerkass, but he's still portrayed in a relatively positive manner - basically a Noble Demon.
Lorenzo de' Medici is portrayed as being a devout republican and a benevolent ruler. In reality, like all the noble families in the Italian city-states, the Medicis were Machiavellian schemers who committed all sorts of immoral acts to maintain their power. If you click the extra-information tab, it's at least acknowledged how he did terrible things. It's shown in the Lineage short how Lorenzo brutally tortures an agent of his enemies for information, and in Brotherhood Lucrezia Borgia claims, probably truthfully, that he quashes the families of his rivals utterly, even those who had nothing to do with the plots against him.
Niccolo Machiavelli's portrayal in the series is closer to his actual biography than to the Hollywood History version that most people know. In reality, he was an ardent supporter of republicanism, and many historians believe that his most famous work, The Prince, was a satire.
Leonardo da Vinci gets an upgrade in heroism, despite only being the sort-of deuteragonist? Notable changes include that his inventions work, are completely functional and can be used at nearly any time. Plus he's the main character's best buddy.
Some inversion in III, particularly showing (reminding) that while patriots of America, figures like George Washington sought to displace natives from the lands fearing their aligning with the British.
Katerina Sforza gets one of these. In the game she is rescued by Ezio. In real life, she was a prisoner of Rodrigo Borgia for over 20 years, in her own castle, and was used on a regular basis by Rodrigo and anyone else he thought might like to. Eventually, she was allowed to enter a convent, swearing to take no further political action against the Borgia clan.
Rodrigo Borgia was certainly a murderous, conniving asshole in real life and as Alexander VI, generally considered to be the worst pope in the history of the Catholic Church; it turns out he was secretly the cackling, monstrous leader of the Templars during the Renaissance. Oh, and he thought Christianity was bunk, but became Pope anyway just for the power.
Thomas Edison was a proven jerkass who regularly stole ideas and performed grotesque "demonstrations" to smear his assistant-turned-rival Nikola Tesla. Turns out he was also a Templar who stole his rival's MacGuffin and gave it to Henry Ford, who in turn, gave it to Adolf Hitler for the express purpose of jumpstarting the Holocaust and World War II. Also, Hitler's conspirators? Winston Churchill, FDR and Josef Stalin. Making matters worse, at some point the Templar Order decided to use a Piece of Eden to cause insanity in Nikola Tesala thus removing him as a threat to both Thomas Edison as well as the general Templar order.
Savonarola in the Bonfire of the Vanities DLC, although AC was hardly the first to come up with this portrayal. He was definitely extreme by modern standards, but people forget that the reason Savonarola was able to carry out his famous Bonfire was because the people of Florence were sick and tired of watching wealthy Italian families flaunt their vast fortunes by commissioning ludicrously expensive sculptures and paintings while the rest of society was beset by plague and poverty. By the standards of the time he was practically a popular revolutionary. Hell, in the 1990s he was even nominated as a candidate for sainthood (he didn't win though, obviously). Notably however, he is not a Templar and even crossed the Borgia, so in Brotherhood one of the Borgia-aligned heralds can occasionally be heard taking a potshot at his reputation.
How Do You Like Them Apples?: The Apples of Eden are one of the more common types of Precursor artifacts; they were used originally as Mind Control devices and are highly sought by the Templars for that reason. Unrelated to the trope, the third game has the exact quote as the title of the achievement for finishing Memory Sequence 3; the more appropriate trope there would be Player Punch.
Averted. You can kill all the guards in a specific encounter and others in different areas won't notice.
In a larger, more metaphorical sense, this is why the Templars keep thriving no matter how many of them are killed by the Assassins—the Templar conspiracy uses society while the Assassins operate outside of it. You can't fight civilization itself, not very well.
It's All About Me: Many characters who defect to the Templars (including the Crusader, the Sentinel, and Lucy Stillman) do so not so much because they believe in the Templars' cause or methods, but to avenge some perceived betrayal against themselves, their family, or their tribe/clan. Additionally, almost all of them harbor an abundance of arrogance. Every one of them thinks himself special, above all others, and unique in history. This is probably why they all have Suicidal Overconfidence when facing the humanoid murder machines known as Assassins. "Sure, you killed hundreds of guards, knights, nobles, high-placed holy men and emperors... but I'm better than all those other guys!" Every one of them also thinks the world (or the nations they immediately occupy) would be better off with himself in charge.
Leap of Faith: The trademark skill of the Assassins (along with the Hidden Blade), consisting of a swan dive down into conveniently-placed haystacks. All recruits are required to perform this as part of their initiation as full Assassins.
Legacy Character: The basic premise of the games is that Desmond is a convergence of the bloodlines of Alta´r Ibn-La'Ahad, Ezio Auditore da Firenze (who are not related to each other despite the implications of the second game), and Connor/RatohnhakÚ:ton.
Nearly everyone in the games who is either an Assassin or a target of an Assassin has amazing free-running skills, even people you wouldn't expect to like overweight (and heavily dressed) Church officials. Assassins Creed III takes it a step further by moving from urban settings to colonial and forested environments; thus the moniker "tree-running".
This series became the Trope Codifier for video games. Many games previously had some sort of building-scaling, but AC was the first game to have the character actually reach out to various handholds and footholds on what would otherwise be something completely impassable, even for Batman. Follow the Leader kicked in; inFAMOUS and The Saboteur are two of the bigger ones.
Like Reality Unless Noted: Most of the time, it's a straight-up Historical Fiction...right up until strange, almost-alien artifacts appear. The fact that the games focus 95% of the time on the historical period helps to drive home just how wrong these artifacts are for intruding into human history.
"Alta´r" is Arabic for "the flying one" or "the flying eagle." Alta´r is also the name of the brightest star in the constellation Aquila, which is Latin for "Eagle". In full: Alta´r Ibn-La'Ahad is "Flying Eagle", "Son of None".
"Miles" means "soldier" in Latin.
The Italian name "Ezio" derives from the Greek word aetos, which means "eagle".
'Animus' is Latin for "soul", and in Modern English usage it can refer to a grudge or purpose.
Malik Al-Sayf is Arabic for "King of Swords".
"Connor" means "Wolf Kin" or "Lover of Wolves" which reflects on his more predatory Assassin style.
The E3 trailer for the first game shows Alta´r assassinating a Templar who is about to hang someone, shooting his bodyguard with a crossbow on the way. Nothing of the sort happens in the game, and crossbows are not available until Brotherhood.
The trailer for AC II shows Ezio chasing and shooting a masked Templar with his Hidden Gun during Venecia's Carnevale. Said Templar only appears in multiplayer, nowhere to be seen in the actual game, although a similar assassination does happen, but with a different victim and very different circumstances.
Brotherhood's trailer shows Ezio challenging and fighting Cesare head-on in Rome; no such scene occurs in the game, and when you do fight Cesare, your Assassin Recruits are not available to help.
Averted with Revelations, whose trailer is the only one to show a canonical scene; in this case it doubles as the game's introduction.
In the AC III trailer, Connor charges a British firing line head-on and assassinates their commander. This appears to be based on an early draft of the Battle of Bunker Hill, but trying to complete that mission in the fashion Connor did in the trailer is impossible.
Mobstacle Course: Fortunately, you can shove them away. In the second game, Ezio can create these with well-aimed money tosses. It's a pretty convenient way of blocking pursuing guards for a few seconds while you're running away. In Revelations, Ezio can use a Pyrite Bomb to scatter fake coins at a distance, distracting guards and civilians alike.
Morale Mechanic: Brutally kill a few guards and some or all of the rest may flee.
Motive Decay: Ironically, this happens to the Assassins. Initially a society devoted to achieving peace through individual freedom and personal responsibility, over time they found themselves increasingly dedicated just to opposing the Templars, with their lofty ideals all but forgotten. They are called on this during Assassins Creed III, both by the Templars and, at the end, by The Ones Who Came Before.
Happened to Templars as well, during the rule of the Borgia. Robert de Sable was Well-Intentioned Extremist. Haytham Kenway is even more well intentioned, and less extremist. However, Rodrigo Borgia is using Templar agenda to achieve his dreams of unlimited wealth and power, while he is enjoying fun of incest, pedophilia or incest pedophilia...And Caesare is no better.
Motive Rant: Most of the primary mission targets, upon being taken down, deliver a lengthy monologue about why they did what they did and why you're a terrible, misguided person for opposing them.
Multi-Melee Master: All the Assassin characters are equally adept at any weapon they pick up, whether it be a knife, sword, axe, mace, etc.
The Assassins, both in the past and present. While the 1191 Assassins seem fairly close to the historical Muslim sect, the Assassin Tombs that can be visited in Assassin's Creed II house the remains of Mongol, Chinese, Roman, Egyptian, Persian, and Babylonian Assassins. Assassin's Creed III' and Assassin's Creed III Liberation add Native American, British, French, and African to the mix. The Templars can also be seen as an evil version of this.
On start-up, the player is assured that the game was created by one of these.
Murder Is the Best Solution: Somewhat ironically, it's the Templars who seem to immediately default to Murder Is The Best Solution when faced with any problem, whereas the Assassins (who are defined by the fact their purpose is to murder people) appear at least to some degree to be willing to pursue alternative solutions including diplomacy or guile (Altair and Al-Mualim have a couple conversations in which it's suggested they only resort to assassination against people who are simply too stubborn or fanatically to be talked out of their harmful course of action), and only resort to murder when no other options are reasonable.
Older Than They Think: In-universe. The Templars and Assassins are way older than either of those Middle-Ages names suggest. There has always been some group trying to take over the world and some other shadowy group trying to stop them by any means, going at least back to ancient Rome and ancient Egypt. Even if one side gets completely wiped out, someone somewhere will come up with the same idea to start it up again (resistance movement or dominate-the-world).
Olympic Swimmer: Starting with the second game, all playable characters can swim perfectly and for any length of time without tiring, no matter how much armor they are wearing, except that they can't hold their breath forever underwater. Assassins Creed III adds an apparent immunity to hypothermia and/or frostbite.
Only to a certain extent, however; in one side mission of AC 3, the player gets desynchronized if they stay in the icy water for too long.
Omniscient Morality License: Having failed at it the first time around, Those Who Came Before grant this upon themselves in service of stopping humanity from being wiped out in 2012. The long struggle between the Assassins and Templars, all the wars and suffering, is part of their plan. Ezio very nearly hangs a lampshade on it in Revelations.
Ezio: Maybe you will be the one to make all this... suffering worth something in the end.
Then it turns out in III that not all of it was their plan. Minerva contemptuously states that mankind squandered her peoples' gifts and warnings in their petty feuds. At the very least, she never planned on the Assassin-Templar feud.
Every game has an opening sequence in which the protagonist performs a Leap of Faith.
Optional Stealth: The series is like this most of the time. There are some missions that desynchronize you for being detected, but by and large it's just as doable to fight all the guards as it is to sneak past them or stealth-kill them.
There's also the first Assassins Creed game, and the second one, for the most part. Later ones have tended to avert this by punishing being caught with game overs.
Order Versus Chaos: The conflict between the Assassins and the Templars is a somewhat nuanced version of this. The Assassins' ultimate goal is to safeguard human freedom, even if that means performing the occasionally necessary evil (assassinating people dangerous to human freedom), and also means allowing humanity to make their own mistakes. At the same time, they live by a strict code (the titular Assassins Creed) which, among other things, prohibits the killing of innocents and encourages them to seek inner peace. In contrast, the Templars want to end human suffering by bringing an end to free will and creating a society of perfect order. At the same time, their belief that there is no afterlife and thus no higher law means that they are free to do whatever they want in pursuit of this goal, up to and including the slaughter or enslavement of millions if it will save millions more in the long term. The Templars' complete lack of any moral rules beyond their singular Utopia Justifies the Means goal seems to explain why the organization is overwhelmingly made up of monsters.
Plague Doctor: In one of the games one of the playable characters is dressed as a Plague Doctor. Assassins Creed II and II:Brotherhood also have NPC doctors in this costume (which is appropriate for Medici-era Italy).
Professional Killer: They are called Assassins for a reason. All the games, however, explore the morality of being a person who literally kills for a living — in Alta´r's case, the question is whether his blind allegiance to his Creed makes him Not So Different from his enemies; while in Ezio's case, the question is just how much death is justified in the service of vengeance; Connor wants freedom, but those around him are too busy fighting to notice the chaos around them. Notably, the characters come to very different conclusions.
Sofia: This is not your battle. Ezio: But where does one end, and the next begin?
Puzzle Pan: Used extensively in the various platforming sequences, especially in the vaults/tombs/crypts that are puzzle-based rather than stealth-based. A minor version is used whenever the game wants to call attention to a particular jump you're supposed to make, frequently resulting in Stop Helping Me! as it screws up the directional controls.
Ragnarok Proofing: Invoked; the First Civilization designed the Pieces of Eden and the Vaults that house them specifically to withstand the ravages of the 75,000 years that have passed since the First Catastrophe.
Refuge in Audacity: When Thieves steal from people, they openly run up to them and do the deed visibly. No one protests. But when Ezio does it sneakily, the victim can somehow recognise him and try to fight back.
Research, Inc.: Abstergo does research and helps fund a secret society.
Scenery Porn: Panning over beautiful vistas of old-world cities is a series mainstay.
Shown Their Work: Throughout the series, Ubisoft shows a remarkable amount of detail into the various historical settings, from the people and their mode of dress to the architecture. Sometimes they use broad strokes to distort history, but this is more often a case of Rule Of Cool, Rule of Drama, or some of the exigencies ofthe video game medium than any deliberate error (for example, almost all doctors in Renaissance Italy dressed up as Plague Doctors because that getup is both extremely freaky-cool looking, and produces an easily identifiable figure/silhouette so the player can find medicine-and-healing-dispensers quickly and easily).
Shout Out: The games love to reference Mario, especially the Ezio series.
In Assassin's Creed II, Uncle Mario introduces himself to Ezio with It's-a-me, Mario!.
Stop Helping Me!: In the platforming sequences, the camera will often helpfully pan over to demonstrate your intended jump, but throws off your directional controls since they are relative to the camera, not the character.
Super Drowning Skills: In the first game, Alta´r desynchronizes if he falls into any body of water higher than his knees. This is lampshaded in the second game as a glitch in the Animus 1.0, and the main characters in II and all subsequent games are very capable swimmers no matter how much armor they wear. In none of the games, however, do civilians or guards learn to swim; nor do your Assassin Recruits, who variously die (Brotherhood), despawn (Revelations), or get injured (III) upon touching water.
Talking Is a Free Action: Each and every primary assassination target gets to have a Just Between You and Me conversation with the player character, regardless of the circumstances under which they were killed. Said conversation takes place in the Animus' White Void Room, implying that the VR reconstruction of the event did not precisely match the actual memory.
The Three Faces of Adam: Ezio's trilogy closely follows this, with ACII, Brotherhood, and Revelations respectively showing the Hunter, the Lord, and the Prophet phases of his life.
Translation Convention: This is in effect for any historical segments shown that do not take place in the Animus (such as the short films Lineage and Embers.)
Translator Microbes: The Animus automatically translates any foreign dialogue that takes place in it for the sake of the user (and the player). It doesn't do it perfectly, though, which gets a bit of Lampshade Hanging.
Two Part Trilogy: Averted. While each game ends on a Cliffhanger or Sequel Hook of some sort, the stories being told in each game is distinct. In fact you could consider Assassins Creed II as itself being split into three parts including Brotherhood and Revelations, linked together as Ezio's story. Supporting this is that once the series moves on to a new main protagonist it goes back to numbering the sequels.
What the Hell, Hero?: While the Assassins are usually portrayed as a force for good, they have also committed their share of moral hypocrisy. This includes hunting down former Assassin Nikolai Orelov and his family, allying with the Ottoman Empire and supporting its conquest of Eastern Europe, while Desmond Miles' father was physically abusive to 'toughen him up'. Altair points out further contradictions in his Codex; they kill whoever opposes them while declaring to support the freedom of humanity (which presumably would include being free to make wrong choices).
White Void Room: The Animus loading screen. The original Animus screen featured lots of hexagonal lines and bits of code]] scattered in the background, while Rebecca's Animus 2.0 had a simpler but cleaner white void with grid lines dividing up the empty space. The Animus 3.0 loading screen is a chaotic void of cloudy triangles.