Which Assassin's Creed game introduced the dialogue-choice system and multiple endings?

Assassin's Creed Odyssey introduced the dialogue-choice system and multiple endings.

Released in 2018, Assassin's Creed Odyssey lets players choose between siblings Alexios and Kassandra and make dialogue decisions that affect quests and relationships. Those choices contribute to different possible outcomes, including several endings to the game's family storyline. This role-playing structure is one of the clearest ways Odyssey differs from earlier entries in the main series.

Assassin's Creed Origins introduced a large open world and stronger role-playing elements, but it did not use Odyssey's branching dialogue and multiple-ending system to the same extent. Assassin's Creed Valhalla continued and expanded choice-based storytelling after Odyssey, which can cause confusion about which title introduced the feature. Odyssey is set during the Peloponnesian War in ancient Greece and includes historical figures such as Socrates and Pericles, while its central playable hero is a fictional mercenary descended from the Spartan king Leonidas.