- "I figured, either I die alone on the streets of Edinburgh, or I die alone, out there in the world somewhere. Didnae see much of a difference. But the Assassins changed my outlook completely [...] Not one of them has ever looked at me like I was a thing."
- ―Eric explaining his reason for joining the Assassins, 2014.[src]
Hailing from Scotland, Cooper was in a relationship with someone who was murdered during a discriminatory attack. After systematically and vengefully hunting down and killing the hate group responsible in Edinburgh, Cooper considered ending his life, but he was recruited to the Assassins by Gavin Banks, who gave him a new purpose.
Welcomed wholly aboard the Altaïr II, Cooper became close friends with Stephanie Chiu, due to his regular hormone check-ups, and Emmett Leary, whom he closely supervised because of his laidback nature; it was to the latter and William Miles that Eric expressed his intention to some day resume a normal life in Scotland, for which Emmett often kept track of the ongoing events back home for him.
Mission to Japan
On 11 September 2013, during an onboard meeting with the Assassin leader Gavin Banks and ship captain Susan Drayton – while the Altaïr II made its way to Japan – Gavin declared that his contact in Osaka was not responding. Eric reminded Gavin that their communications had been disrupted since the solar flares in December, but Gavin informed him that he and his contact had their own way to communicate. He then directed Eric to sail to the Philippines, where they bought several weapons for Philippine gun makers in preparation for a possible fight with Abstergo agents.
In December, the Altaïr II arrived in Osaka and the crew discovered the Assassin safehouse had been attacked by the yakuza. After determining the Onmoraki-Gumi were likely responsible, Eric and the other Assassins began investigating the identity of the group's leader. Eric heard that the leader was a 64-year old woman who had killed her own family, and entered into a bet with the other Assassins in that whomever guessed the closest to the leader's identity would win the right to shower first in the morning for a month.
The leader of the Onmoraki-Gumi turned out to be Saeko Mochizuki, the local Mentor of the Osaka Brotherhood who had taken over the organization after it attacked the Assassins, through killing its previous leaders; after discovering this, Eric declared himself the winner of the team's bet and began using up all the hot water in the morning. On 31 December, Eric invited Saeko aboard the Altaïr II for a tour while the team stopped in Tokyo to gather supplies, and assisted her and Susan in cleaning up the messy ship before having homemade toshikoshi soba prepared by Saeko.
Shortly after a mission to Moscow resulted in Russian Assassin Galina Voronina joining the ship as Gavin's enforcer, Eric and the rest of the Altaïr II crew were directed by Gavin to find out where William Miles was hiding from a clue in the latter's journal. They deciphered the riddles within to a hidden cove in Norway, and on 1 May 2014 the Altaïr II arrived at William's whereabouts.
When Rebecca Crane began upgrading the systems on the Altaïr II, she discovered that a spy on the ship was uploading reports to a database run by a group called the Initiates. Eric and the rest of the crew, except for Gavin and Galina, were confined to their quarters on the ship until they could be interrogated and cleared of suspicion by William; Eric was especially surprised that one of the crew could be working against them.
On 10 May, Eric was the fourth crew member to be interviewed by William, answering questions regarding his life in Edinburgh, his incorporation into the Altaïr II and his duties on board the ship. During the interview, Eric noted that discrimination had greatly affected his life. He also mentioned that he had undergone various surgeries and required hormone regulation to maintain his appearance.
On 23 May, William finally called all of the crew members together to announce the identity of the spy. When William named Chiu as the traitor and ordered Galina to kill her, Eric intervened, claiming that he had been the spy all along. The pair then revealed that Eric had been writing the spy reports, while Stephanie had been the one uploading them.
However, to their relief, Wiliam decided not to execute either of them, as the evidence that Rebecca had compiled on the Initiates, along with what he had learned from the interviews, had shown him that the hackers seemed reasonable, and perhaps could be a valuable ally.
- "There are a lot of good people at risk, whose only crime was curiosity. I generally don't have a lot of time for Jasdip's shitty attitude, but he's right on this one. The Initiates aren't like us and they're in danger. Abstergo can make them disappear. Or worse."
- ―Eric in his message to Bishop, 2015.[src]
A year later, Bishop called upon Assassins across the globe to locate the secret laboratory of Álvaro Gramática, an Abstergo scientist that had gotten his hands on a Shroud of Eden. When Jasdip Dhami expressed his reluctance to continue using the Initiates, Eric joined in, reporting that a lot of the Assassins' supporters, from military contacts to financial benefactors, were running into trouble.
He feared that Abstergo was actively targeting the Initiates and felt they needed to do something, as these were not trained members of the Brotherhood, but mere civilians. Bishop would later send out a message, ordering the Initiates to lay low for the time being, though she assured them they would likely hear from her again at some point.