He serves as the protagonist of the 2014 game Assassin's Creed Unity, in which he is portrayed by Canadian actor Dan Jeannotte through performance capture, and voiced by Godefroy Reding as a young child.

Scriptwriter Travis Stout, who wrote the story for the single player campaign of Unity, explains that Arno Dorian is a lead character who constantly questions the Brotherhood of Assassins' legitimacy and belief system.

He created Arno as a "very well educated young man, raised in a noble household, with access to tutors and books, and thus is very well-read", and that he has a tendency to use humor to deflect whenever he is emotionally vulnerable, and habitually quotes classical texts whenever the opportunity arises.

Stout claimed that he "tried really hard" to develop an interesting character that feels like a real person, "the complete opposite of the usual grizzled tough guys spouting one-liners that gamers are used to seeing in action games and movies".

[1] In an interview with Game Informer, Unity creative director Alex Amancio explains the conflict between Arno's character arc and Élise's goal for vengeance.

Arno eventually develops a belief in the Assassins' cause and what they stand for, he is still constantly questioning their methods and refuses to follow their values blindly, especially since the man who raised him and the father of his love interest is a Templar.

Amancio explained that both characters have the same goal though their starting point are based on different reasons: while Élise is purely driven by revenge for the murder of her father, Arno strives for redemption and attempts to find out why it occurred in the first place.

[3] Amancio explained that Arno does not get very involved politically in the French Revolution, with the ideals and extremism of the historical period merely provide a compelling backdrop for his personal struggles.

[3] The Dead Kings downloadable content pack also introduces the Guillotine Gun, an axe that also functions like a grenade launcher or blunderbuss with a long-range attack that strikes multiple enemies at once.

He noted that the producers are open to collaborating with voice actors, and readily take in feedback proposing potential changes to a dialogue line or movement in a certain way.

The head of the family, François de la Serre, is the Grand Master of the French Rite of the Templar Order, but out of respect for Charles Dorian's memory, he never lets Arno know about his father's true affiliations or the circumstances of his death.

Having personally known Charles Dorian and recognizing Arno's potential, Bellec teaches him how to sword fight and invites him to join the Assassin Brotherhood after they both escape during the Storming of the Bastille.

Through his investigation, Arno eventually uncovers the identity of the Templar at the head of the conspiracy: François-Thomas Germain, the leader of a radical faction within the Order who intend to continue the work of Jacques de Molay.

During the later part of the French Revolution and the beginning of the Reign of Terror, Arno works with Élise behind the Assassin Council's back to hunt down Germain and his remaining co-conspirators.

The ending of Unity, which chronologically takes place years later, sees Arno back in the Brotherhood, narrating about how his understanding of the Assassins' Creed has changed and promising to continue protecting Paris.

He initially falls into depression and is no longer interested in being an Assassin, refusing to act when he learns Napoleon plans to retrieve a powerful Piece of Eden from the catacombs of Saint-Denis.

[8] A young Arno appears in the Palace of Versailles during the ending sequence of Assassin's Creed Rogue, in which players control Charles Dorian's killer, the Assassin-turned-Templar Shay Patrick Cormac.

Kimberley Wallace from Game Informer said Arno's personality is a "no-nonsense type with a sharp wit, but he doesn't hesitate to be brutal", and observed that as an Assassin, "he will go for the kill when the situation demands it, and since he only uses a single blade, he gets creative, especially when facing multiple enemies".

[3] She argued that regardless of Arno's tactics, he is a "likeable guy through and through", and claimed that it is "the one comment that has surfaced most as more people at Ubisoft are playtesting the game" prior to its launch in November 2014, and observed that since his world is full of "shades of gray", it forces him to question everything, from his allies to the woman he loves.

[3] Brenna Hillier praised the narrative in Unity as a genuine story due its focus on the characters' personal journey, as opposed to nonsensical content framed by the game's writers to fit an existing set of missions and side-content.

[14] Writing for The New York Times, Stephen Totilo noted that players of Unity no longer have the moral certitude which justifies their player character's efforts as in many other video games, and that the conceit of a freethinking Assassin who occasionally crosses the flawed order that he joined in the first place for the Templar he loves is "a fitting plot for a game set in Paris at the time of the French Revolution, itself a drama of faltering ideals".

[24] French website Gameblog expressed disappointment in response to Jeannotte's unflattering comments about French-accented spoken English, and insisted that the usage of a British accent does not necessarily produce a better aural experience.