Predecessor Villain: They are this to the Templar Order.
Let's just say that killing the son of a Medjay and his wife not only started a Secret War that will last for millennia but it is the main reason why the Assassins even exist.
Nice Job Fixing It, Villain: Their involvement in Khemu's death borders on John Wick-levels of villain stupidity.
Names to Run Away from Really Fast: Most members in the Order have monikers and nicknames that invoke predatory animals (i.e.
Multinational Team: The Order is comprised of Romans, Greeks, Egyptians, Persians and even a couple of Gauls.
For example, once Ptolemy XIII is deposed, the surviving members of the Order curry favor with Cleopatra and Caesar by appealing to their desire to rule an empire. This is what allows the Order of the Ancients to survive and prosper despite the changes in political leadership.
Manipulative Bastard: Members of the Order use their political skills and wealth to maneuver themselves into the favor of powerful people everywhere in the known world.
Malevolent Masked Man: When in disguise, members of the Order wear identical black Egyptian facemasks, black robes, and sandals.
What they didn't expect was that his parents would go on a Roaring Rampage of Revenge that not only got them entangled in the complicated, rigid world of Ancient Egyptian and Roman politics but they would go on to create the Hidden Ones, the precursors to the Assassin Brotherhood. The Order of the Ancients were responsible for the murder of Khemu, the son of Bayek and Aya.
For Want of a Nail: Or rather For Want Of A Child.
For Science!: The original intent of the Order was to conduct research on newly-obtained Lost Technology from an Isu vault.
Exactly What It Says on the Tin: They are a secret order that has existed since ancient times.
Evil Is Petty: In keeping with their Templar successors, they can do pretty evil and ruthless things just for the fun of it.
Even Evil Has Standards: It's implied that at least some of them were rather unnerved by just how ruthless Flavius was in murdering Khemu.
After the true vastness of the Order is revealed, Romans as well as various peoples throughout the known world are revealed to belong to the Order as well.
Equal-Opportunity Evil: The members come from a variety of cultures, including Greeks, Africans and ethnic Egyptians.
Dark Is Evil: Their attire while in disguise is black in color, and they're antagonists.
Create Your Own Hero: Had they never antagonized Bayek and murdered his son, he and Aya would likely have never gone after them and later set things in motion to create the Hidden Ones/Assassin Brotherhood.
The fact that they are able to do so without consequence attests to the amount of power they have over the Egyptian government.
Blasphemous Boast: Their use of pharaonic imagery in their disguises is effectively a form of this.
The organization is even called "the Snake" to some individuals.
The Order as a whole has an animal representing it, the snake, contrasting the Hidden One/Assassin eagle.
Their aliases are based around various animals, and even their death scenes tend to have the animals in question show up around them.
Assassin's Creed: Odyssey's Legacy of the First Blade DLC establishes them as also having been active in ancient Persia somewhere after that.
Ancient Conspiracy: The group is literally ancient in that the founder of the Order was the Egyptian pharaoh Smenkhkare, who discovered the Isu vault Eeyoo Sekedoo Aat around 1334 BCE, and founded the Order in order to better understand the First Civilization.
Aristocrats Are Evil: As founders of what will become the Templar Order, many of the members of this organization are influential citizens in their respective societies, consisting of government officials, generals, priests, wealthy merchants, and other social elite which have connections to the likes of Cleopatra, Ptolemy XII, and Julius Caesar as well as other royals in the ancient and medieval eras of history.
Their symbol is a serpent wearing the Double Crown of Egypt with an ankh. A shadowy group of influential people that seeks to control Egypt and eventually the rest of the world.