A medieval setting could be the shot in the arm that the Assassin's Creed franchise needs. The series has lost the plot, going from fighting for freedom against all odds in its early iterations to protagonists that literally appoint tyrants to rule.
Think back to a time when feudal lords ruled over serfs with an unjust hand. They claimed to be divinely sent, only to do the bidding of evil. Now that's a front where the Assassins and Templars need to reignite their feud. Some of these situations are just perfect for Assassin's Creed fans.
The medieval period specifically refers to the western world (Europe, Northern Africa, and the Middle East) between the 5th and 15th centuries. No disrespect is intended toward other areas in the post-classical period around the globe.
10 Constantinople - 5th Century
Now known as Istanbul, Constantinople was the capital of the Byzantine Empire at the start of the medieval era. It is home to the Hagia Sophia, a church building with plenty of intrigue. Assassin's Creed has already left so much awesome history out of their games, it would be a shame to not explore this area at some point.
King Justinian I is the perfect template for a templar, as writer Procopius described him as "deceitful, devious, false, hypocritical, two-faced, cruel, skilled in dissembling his thought, never moved to tears by either joy or pain, though he could summon them artfully at will when the occasion demanded, a liar always, not only offhand, but in writing, and when he swore sacred oaths to his subjects in their very hearing."
9 Rome - 5th Century
At the onset of the dark ages, Boethius gave the world its most stern warning in an attempt to prevent what would overshadow all of Europe for the next century. After personally revealing the corruption within the legal system, he wrote The Consolation of Philosophy, a work that reconciles the teachings of Plato, Aristotle, and Christ.
Despite suffering from depression and awaiting his ultimate execution, he found joy in life, writing about everything from music and theology to math and science. Truly a member of the Assassins, his fight to expose dirty politicians would make for an excellent game.
8 Iran - 6th Century
To oppose the aforementioned Byzantine Empire was Khosrow I, known as the Philosopher King. The Sasanian emperor successfully repel the invasion, though the kingdom would fall after his rule one century later.
During this time period, Iran grew in matters of culture and economy despite the military assault. This was an amazing accomplishment, one that could easily have been the doing of Assassins taking out Templar invaders.
7 Carolingian Empire - 8th Century
Although not many people are familiar with the Carolingian Empire, the Franks, or the Lombards those who haven't taken history classes have surely heard of Charlemange at least. An open-world Assassin's Creed game would be awesome here as the area covered virtually all of central Europe.
Charlemange is a complicated figure. He was, of course, still an emporer. But he is described as having "unremitting physical energy and intellectual curiosity." He could be one of the most successful Assassins of all time.
6 Northern Italy - 11th Century
There is an obscure event in history called the Walk to Canossa. After Emporer Henry IV abandoned his duties to the Catholic Church, Pope Gregory VII excommunicated him and revoked his position as king. Henry then reportedly begged outside of the gates for three days to be restored.
Henry was eventually permitted to rejoin the Church, but Gregory did not give his political power back. There are many blanks to fill in with this story, adding some cool Assassin insignias to the era would make it even better.
5 France - 11th Century
The tragic love of Peter Abelard and Heloise d’Argenteuil is one that seems directly influenced by the Assassins. Peter Abelard came up with the concept of limbo and the moral influence theory of atonement, paining God in a compassionate light.
Heloise d’Argenteuil was a woman who learned to read and write, escaping an abusive situation and powerfully speaking out against the establishment. Not all Catholics were tyrannical monsters and this story would show struggle or even infiltration within the Templar order. It's the perfect amount to explore in a shorter Assassin's Creed game.
4 Morocco - 13th Century
Notable Islamic conqueror Saladin would be joined by Jewish scholar Maimonides across northern Africa. Their unlikely unity to conquer large chunks of the world could be the doings of the Templars, who would twist faith in exchange for power.
However, both figures are not one-dimensional. Saladin gave his wealth away to those he loves and Maimonides would The Guide for the Perplexed to help bring greater understanding to the less fortunate. A video game writing team would have a field day explaining what might have happened.
3 Mali - 14th Century
When adjusted for economic variations over time, it's often believed that Mansa Musa was the richest human being that ever lived. Although recognized as the King of Mali, Musa was highly mobile, moving his entourage all over northern Africa and up through Egypt.
It's not well known what Musa's intentions were. By giving away mass sums of gold, he often brought on scholars and established learning centers. This kind of motivation would be ideally explained by a battle for the people against the Templars.
2 France - 15th Century
Joan of Arc may be the most popular figure from this period and her role as both a female and teenage combatant is worth exploring, especially from an Assassin's Creed game. But the Hundred Years' War during this era has even more depth than her journey alone.
The war lasted for 116 years, ending with the English finally, but briefly, taking control of France. So long as the game avoids some of the more frustrating missions within the franchise, there are more than enough stories to explore.
1 Germany - 15th Century
Perhaps the most interesting story of the medieval period is the one that ended it. For over one thousand years, literary supremacy allowed tyrants to keep history and religious teachings to themselves. When Johannes Gutenberg invented the printing press, that ended.
Gutenberg and his allies not only had to invent technology that could distribute literature, but they also had to invent a written language that matched the people's spoken language. This group that included Martin Luther blew the lid off of monopolies on information. This would thwart the Order of Ancients as they became the Templars.