In his youth, Barnabas was a soldier before turning to commercial shipping for a livelihood. In this capacity, he developed a network of contacts throughout Greece, including local leaders and mercenaries, who became a primary source of information for Kassandra. By offering his ship and crew to the Spartan mercenary, so that they might first leave Kephallonia, the two befriended.
At some point, Barnabas met Leda, a native of the Greek island of Ithaka, and they fell in love, eventually marrying. They also sailed together regularly.
One night during a siege, Barnabas' fleet was destroyed during a storm. During the same incident, Barnabas claimed to have come face to face with Poseidon's "murderous pet", and lost his eye to it. As their ship was wrecked, Leda roped together the remains and together she and Barnabas paddled to a shore.
However, the two were separated. Later, Barnabas left the navy, and became a sailor in his own right, eventually rising to be the captain of his own ship, the Adrestia.
- Barnabas: "I can't thank you enough. After spending most of my life at sea, it would have been absolutely shameful to drown in a pot! Ah, where are my manners? I am Barnabas, captain of the Adrestia."
- Kassandra: "Well, Barnabas. I am pleased to meet you. I'm Kassandra, misthios by trade."
- ―Barnabas meeting Kassandra for the first time, 431 BCE.[src]-[m]
In 431 BCE, Barnabas visited the island of Kephallonia and docked at the town of Sami. While exploring the island, he met the Cyclops of Kephallonia and told him of a tale he had heard during his last voyage. When Barnabas mentioned the words "one-eyed monster", he was kidnapped by the Cyclops to Kleptous Bay, unaware that the words were considered sensitive to the Cyclops.
The Cyclops repeatedly dunked Barnabas' head into a vat of water, only stopping after he was confronted by the misthios Kassandra. Kassandra eliminated the Cyclops and his men, bringing Barnabas to safety outside the bay. After introducing himself and telling his stories, Barnabas agreed to lend his services and ship to Kassandra, who was in need of a ship to travel to Megaris. Barnabas informed Kassandra to meet him back in Sami whenever she's ready to depart.
As they departed from Sami, Kassandra told Barnabas to set sail to Megaris, as he had a contract from Elpenor to eliminate the Wolf of Sparta. As Barnabas mentioned the Wolf to be Nikolaos, Kassandra revealed that Nikolaos was her father.
Unmasking the Snakes
After Kassandra confronted her father, she returned to Barnabas to discuss what he had told her, namely that her mother was still alive and to beware of "snakes in the grass." Barnabas counseled her to seek out the Oracle of Delphi, as they were on their way to Phokis anyway to report back to Elpenor. He cautioned her to make extra preparations, as Nikolaos' words had put her on guard.
After her meeting with Elpenor turned hostile, Kassandra reunited with Barnabas outside the Temple of Apollo, where he introduced her to Herodotos, to whom he had already divulged a great deal of information about Kassandra herself, including her spear. She admonished him for being so trusting with strangers, after which they all discussed the question Herodotos asked of the Pythia how to end the war. Kassandra recognized her answer, "Spring should not wish for winter, as it brings death with it," as a threat, to which Barnabas simply replied she was on Kephallonia for too long. They discussed the long line leading in to see the Pythia, to which Barnabas suggested Kassandra simply walk in, asking rhetorically who would stop her. Kassandra agreed and marched inside the temple.
After Kassandra killed Elpenor and investigated the Cult of Kosmos, she met with Herodotos at the Lion of Leonidas at the Hot Gates of Thermopylai in Malis, to test his theory regarding the Spear of Leonidas. Afterwards, Barnabas welcomed Herodotos aboard the Adrestia as a traveling companion. They revealed to Barnabas that the Cult was controlling the Pythia's words, and through her, the Greek world, which shook the pious sailor to his core. Nevertheless, he boasted of Kassandra's own greatness and expressed his belief that they would bring the "wrath of the gods" down on the Cult. He ordered the men onwards to Andros, and then to Athens, to continue their investigation. 
An Odyssey Across the Aegean
After Kassandra attended the symposium in Athens, Barnabas regularly shared council with her as they sailed to Argolis, Korinthia, and Keos, the locations she was given as the best potential leads on her mother's whereabouts. She shared what she had learned in each region, as well as explaining the nature of the Cult's activities therein. Each time, Barnabas would reaffirm his confidence in Kassandra's abilities.
Their partnership took them to every island on the Aegean Sea, especially Naxos in the aftermath of the Plague of Athens of 429 BCE, where Kassandra had finally learned her mother had taken up residence. As they sailed towards the island, Barnabas sensed her nervousness and reassured Kassandra that any mother would be proud to have someone as brave and loyal a daughter as her.
After their meeting, Kassandra reported back to Barnabas that even Sparta had fallen into the Cult's grasp, as they sailed towards Paros to undermine their campaign against Myrrine and Naxos. Barnabas vowed to sail with her to Sparta once Naxos was secure.
With Naxos secure, Kassandra eventually sailed into the harbor at the Village of Gytheion in Lakonia to reunite with her mother on Spartan soil for the first time in nearly two decades. The bay felt familiar to Kassandra, and Barnabas remarked that "a bird can fly away for seasons, but it will always recognize its nest when it returns." Kassandra doubted that she was welcome there, but Barnabas replied "when the time is right, we always get to go home." Kassandra asked where home was for him, a story he chose to save for another day.
Around 428 BCE, Kassandra returned to Sparta, where Pausanias, one of the two kings of Sparta, tasked Kassandra with escorting the Spartan Pankration champion Testikles to the Olympic Games in Elis, in order to prove her loyalty to Sparta and redeem her family in the eyes of the gods. During the journey from the island where Testikles trained to Elis, Barnabas praised his performance in the previous games. Unfortunately, the champion died shortly after disembarking at Kyllene, after he stumbled drunkenly off the docks into the maw of a nearby shark, and at Alkibiades's urging, Kassandra became Sparta's champion at the Olympics in his stead.
Once they had reached the Sanctuary of Olympia, Barnabas was more than happy to give Kassandra a tour of the city, while telling her about the history of the Games and traditions associated with it.
During the Olympics Alkibiades participated with a number of others in a habitual celebration hosted by his old friends and Olympic judges Kallias and Demophanes. Soon afterwards, he fell ill, and while Barnabas looked after him, Kassandra investigated, finding the other participants dead...save for Kallias. She followed clues to the merchant Priam, who led her to the antidote, which saved Alkibiades' life.
The Delian Rebellion
Kassandra received a missive from Kyra, a rebel on the island of Mykonos, requesting her aid in her rebellion against Podarkes, leader of the Silver Islands, and the Athenians who backed him. Barnabas indicated that he was a member of the Cult of Kosmos, which spurred Kassandra onwards to the islands. Arriving at Mykonos, Barnabas explained the mythical history of the islands of Delos and Mykonos, as well as provided her a warning of the cruelty of Podarkes himself.
Taking Back Athens
After Kassandra's Spartan birthright was restored, she sailed to the Battle of Pylos, where she briefly fought against her brother Deimos. They were knocked unconscious by falling trees and she was captured, taken back to Athens and imprisoned, where Kleon taunted her. Barnabas stormed the prison armed with only a shovel and Sokrates at his side in an effort to liberate her, only to find that Kassandra had already defeated the guards Kleon left behind to kill her. The two men quickly returned her equipment and instructed her to meet with the Periklean Circle at Perikles' Residence, where Kassandra set her sights on undermining Kleon's popularity with the people, and therefore his authority.
Dinner in Sparta
With Kleon dead at the Battle of Amphipolis, the Cult of Kosmos routed, and her remaining ordeals with her family resolved, Kassandra sat down to a meal in her childhood home. Afterwards, Barnabas joined her on the hill overlooking the city and discussed the outcome of her odyssey. He remarked that wherever her adventures took her next, he and the crew of the Adrestia would be right there with her.
Adventure to Atlantis
Around 424 BCE, Barnabas and Herodotos accompanied Kassandra when she went to Thera to meet her birth father, although he remained on the Adrestia. When she returned and told them her father was none other than the famed philosopher Pythagoras, Herodotos was shocked. After Kassandra had gather the four Atlantis artifacts and sealed the ancient city, she made Barnabas and Herodotos promise never to tell anyone about the place, to which they agreed.
Legacy of the First Blade
Between 429 and 422 BCE, Barnabas traveled with Kassandra to Makedonia to fulfill a job helping someone move. Soon after they arrived, Kassandra spotted a man on fire and determined him to be more worthy of her attention, leaving Barnabas behind with the ship as she traveled further inland. At the village beyond the port of Potidaia, she found herself confronting the Order of the Ancients, who had set fire to the village. She defeated them, and in the process met the Persian Natakas.
After encountering Natakas' father Darius and forming an alliance with the two Persians against the Order of Hunters, she consulted with Barnabas. She told him of Darius' claims, namely that he assassinated Xerxes I of Persia, and the Order had come to Makedonia to hunt her and those like her. Barnabas expressed their situation simply, asking if she believed Darius and trusted him. Regardless of her answers, he advised her to return to the Persians in order to learn what was really going on, as Kassandra noted that Darius was definitely hiding something. He bid her to be careful, to which she quipped she would be as careful as she always was, much to Barnabas' chagrin.
After the Huntsman was slain and the Order of Hunters routed, Kassandra and the Persians parted company, though Darius eventually sent for her after he and Natakas had become stranded in Achaia along with several other passengers due to a naval blockade set up by the Order of the Storm, led by the Tempest. Kassandra reunited with them and they set about weakening the Tempest's forces, including acquiring plans for the Chimera's Breath, a ship-mounted flamethrower capable of wreaking devastating damage in naval battles. Barnabas would become responsible for deciphering the blueprints and making the weapon worthy for the Adrestia to wield.
Kassandra, Natakas, Darius, and their local ally Kleta initiated their plan to liberate the stranded from Achaia. As they watched the first group of passengers sail away, Barnabas ran up to alert them to the massing fleet led by the Tempest herself. Kassandra ordered the Adrestia ready for battle, vowing to smash every ship in the fleet.
At sea, Barnabas had put the finishing touches on the Chimera's Breath installation, making it ready for use in the moment it was needed most. With the flamethrower at their disposal, Kassandra tore through the Tempest's fleet, including her flagship the Skylla. Barnabas could barely contain his excitement and even went as far as to declare Kassandra "Prometheus" for her taming of fire.
After a great deal of time had passed and Kassandra ultimately settled down to start a family with Natakas and Darius, they found themselves once again at the tip of the Order's sword. Their assault devastated their home village of Dyme, Natakas was murdered, and his and Kassandra's son Elpidios was kidnapped by the Order of Dominion. Darius abandoned Kassandra to pursue the Order by himself, and Barnabas eventually arrived to provide his condolences to his captain and friend. He had deduced that the siege weapons used by the Order could only have been produced in Messenia, providing Kassandra a vital clue to pursue the Order herself and bring her wrath down upon them.
Personality and characteristics
Barnabas strongly believed in the Greek gods and the old legends of heroes and mythical beasts, as well as that everybody's fate was predetermined by the gods. He also believed that the Pythia could never be controlled by anyone but the gods and was shocked upon the revelation that anyone could. He also respected Kassandra's role, believing the gods set her upon this. He also has a habit of pointing out the mythical information of certain areas like Marathon.  Barnabas was also a kind and cheerful man since he almost never makes any complaint in a completely calm state.
Barnabas is known to have courted at least three women during his lifetime. Sometime in the early 400s BCE, Barnabas was married to a woman named Leda of Ithaka. However, they were separated, and he lost track of her. He also unknowingly fathered a child with Leda, also named Leda, whom he reconnected with almost thirty years later.
Around 428 BCE, Barnabas took a liking to a widowed Naxian woman, Photina, during the months Kassandra and her mother reconnected with each other. Barnabas even allowed Photina to tattoo his back and braid his hair. As a parting gift and as a token of their short love Photina gave Barnabas an medallion, previously owned by her husband. Barnabas called the medallion "a piece of Pythagoras' wisdom." While the two enjoyed each other's company, Barnabas' seafaring lifestyle led them apart.
Some time later during the later 420s BCE, Barnabas met Iola at the Sanctuary of Apollo on the island of Delos, and according to them, it was "love at first sight." Later, they celebrated the Silver Islands' liberation together. Iola also took to calling Barnabas by a pet name "Barney." Kassandra then offered Iola to join their crew, and Iola accepted. When Barnabas met his daughter he told her of Iola and wanting to introduce her.
- ↑ Assassin's Creed: Odyssey
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Assassin's Creed: Odyssey – The Big Break
- ↑ 3.0 3.1 Assassin's Creed: Odyssey – Odyssey Into the Past
- ↑ 4.0 4.1 4.2 Assassin's Creed: Odyssey – Daddy's Home
- ↑ Assassin's Creed: Odyssey – Onwards to Phokis
- ↑ Assassin's Creed: Odyssey – Consulting a Ghost
- ↑ Assassin's Creed: Odyssey – Memories Awoken
- ↑ Assassin's Creed: Odyssey – Island of Misfortune
- ↑ Assassin's Creed: Odyssey – A Mother's Prayers
- ↑ Assassin's Creed: Odyssey – Quarry Quandary
- ↑ Assassin's Creed: Odyssey – Home Sweet Home (Odyssey)
- ↑ Assassin's Creed: Odyssey – Delivering a Champion
- ↑ Assassin's Creed: Odyssey – Barnabas Abroad
- ↑ Assassin's Creed: Odyssey – The Long Game
- ↑ Assassin's Creed: Odyssey – Trouble in Paradise
- ↑ 16.0 16.1 Assassin's Creed: Odyssey – A Night to Remember
- ↑ Assassin's Creed: Odyssey – Doing Time
- ↑ Assassin's Creed: Odyssey – Dinner in Sparta
- ↑ Assassin's Creed: Odyssey – A Family's Legacy
- ↑ Assassin's Creed: Odyssey – Atlantis Destroyed
- ↑ Assassin's Creed: Odyssey – The Horsemen Cometh
- ↑ Assassin's Creed: Odyssey – More Questions than Answers
- ↑ Assassin's Creed: Odyssey – Tides of War
- ↑ Assassin's Creed: Odyssey – Calm Before the Storm
- ↑ Assassin's Creed: Odyssey – Leviathan's Maw
- ↑ Assassin's Creed: Odyssey – A Flight in Fire
- ↑ Assassin's Creed: Odyssey – Consulting a Ghost
- ↑ Assassin's Creed: Odyssey novel – Chapter 11
- ↑ Assassin's Creed: Odyssey novel – Chapter 12