- "It's the eyes that mark him."
- ―Edward Kenway, describing the Sage Bartholomew Roberts, 1716.[src]
Notable Sages included Templar Grand Masters Jacques de Molay and François-Thomas Germain, carpenter and explorer Thomas Kavanagh, Jr., pirate Bartholomew Roberts, and Abstergo Entertainment employee John Standish, as well as an unidentified Templar Master Spy working for Germany in World War I London and Elijah, the son of Desmond Miles, a young boy who, as of 2015, lives in New York City with his mother.
- "You see, Richmond, being a Sage means Aita, Isu scientist - husband of Juno herself - hid his memories in your DNA, and it has bubbled up to the surface. Aita does not care about you, and the surfacing of his memories drives most Sages mad."
- ―The Sage Elijah, explaining his abnormal nature, 2017.[src]
Sages are typically born with personalities and memories of their own, but they also possess the memories of Aita, which usually manifest themselves as visions at some point during adulthood and later throughout a Sage's life, although it is not uncommon for these visions to manifest during one's childhood. The process is described as a very traumatic experience, with the individual believing they are going mad as their own memories and personality are gradually merged with Aita's own. Some Sages like Jacques de Molay eventually found some mental stability, but the majority of them became erratic and somewhat mad. Others, such as Kavanagh, tried to resist the change, albeit with limited success, holding on to their former selves by constantly keeping the new memories at bay.
The Sages bear a strong physical resemblance to Aita, and usually possess a distinctive combination of anisocoria and heterochromia. Despite being very close in appearance, the Sages came from diverse genetic and ethnic backgrounds and do not always express the same parts of Aita's DNA and as a result are not clones. For example, Jacques de Molay did not display heterochromia, unlike other known Sages. Although only male Sages had been identified by 2015, the Assassins believed that there was a small chance that the recessive gene creating a Sage could also manifest itself in a female individual.Sages are also noted for their above-average intelligence, capable of picking up concepts alien to their upbringing and cultural background easily, and displaying exceeding talent in one way or another.
According to Abstergo, while the genome of an average human contains 0.0002% to 0.0005% of First Civilization DNA, the concentration reaches from 5% to 6% in the genome of Sages. In comparison, the most gifted human recorded, Desmond Miles, had a count five times lower, potentially giving the Sages an unmatched access to Eagle Vision and an exceptional affinity with Pieces of Eden.
Around 75000 BC, in an attempt to save Earth from a solar flare, Aita had volunteered to be a test subject of one of the solutions meant to prevent their civilization's destruction. His wife, the Isu scientist Juno tried to replicate some of Consus' work, by transferring Aita's consciousness into a more resistant synthetic body but Aita died in the attempt.
However, before her imprisonment in the Grand Temple, Juno managed to manipulate the human genetic code, implanting a hidden trigger that would randomly activate and alter the genetic makeup of the individual, changing their appearance and imbuing them with Aita's memories, partially reviving her husband in a human form, again and again for millenia.
Instances of Sages have been recorded throughout the known human history, in various regions around the globe. According to Bahlam, an Assassin Mentor and the father of Ah Tabai, there had been at least eight recorded Sages by the late 1600s, although several Abstergo Entertainment researchers later concluded that the real count was likely much higher.
A Sage's blood is required to open the passage to the Observatory, hidden in Long Bay, Jamaica, through inserting it into a blood vial. The Mayan civilization and Taíno people worshiped the Sages, and the Mayan ruins in Tulum, Mexico contained a statue resembling a Sage's head.
Throughout the centuries, some Sages stayed true to Aita's memory and love for Juno, forming cults venerating the Isu and praying for their mistress' return. The latest iteration, the Instruments of the First Will, was active during the 21st century.
Return of Juno
In 2012, following Desmond Miles' sacrifice in the Grand Temple which prevented the second solar flare from destroying the Earth, Juno was freed from her imprisonment, and integrated herself into the planet's digital network. A 21st century Sage, John Standish, began to search a suitable host for her, eventually deciding on an Abstergo Entertainment analyst. However, after an unsuccessful attempt of offering the analyst to Juno in the bunker beneath Abstergo's Montreal facility, and an attempt to poison the analyst afterwards, Standish was killed by security, and his body was taken by Abstergo.
During the following year, Abstergo scientists researched John's body, and focused on searching for other Sages throughout history, initiating the Phoenix Project to create a complete genomic map of Isu DNA and unlock the secrets of the Pieces of Eden through exploration of Sages' genetic memories. However, the Assassins recruited several Helix users to thwart the efforts of the Templars, and attempted to find the remains of past Sages before them.
In October 2015, Elijah–the illegitimate son of Desmond Miles–was brought to an Abstergo clinic, where his lineage, and the fact that he was a Sage, was discovered. Álvaro Gramática wanted to have him kidnapped and dissected for study, but Isabelle Ardant immediately refused, believing it would be better to put the boy in an Animus for fifty years and study his lineage. Ardant was killed before this plan could be enacted, however.
Elijah would go on to work with the Instruments of the First Will – a group who sought to return Juno to a physical body by using Abstergo's Phoenix Project. Because of lineage, Elijah possessed a markedly higher concentration of Isu DNA in his genome than other Sages, which enabled him to resist Aita's personality from taking over, while taking advantage of Aita's memories and knowledge. Elijah used Aita's knowledge to continually sabotage Juno's efforts at resurrection, and eventually assisted in her final death. 
Individuals speculated to be Sages by Abstergo Industries are marked with an asterisk. (*)
- Other individuals displaying heterochromia are featured in the franchise, namely Alexander the Great, the Son of Ra and Ojeda. However, despite evidences suggesting that they were Sages it has yet to be confirmed.
- Assassin's Creed IV: Black Flag (first appearance)
- Assassin's Creed: Unity
- Assassin's Creed: Syndicate
- Assassin's Creed: Uprising