Which Assassin's Creed game introduced the RPG dialogue-choice system that can alter its story?

Assassin's Creed Odyssey introduced the RPG dialogue-choice system that can alter its story.

Odyssey lets players choose between Kassandra and Alexios as the protagonist and presents conversations with selectable responses. Some choices affect relationships, quest outcomes, character survival, and the ending, giving the game a branching structure that was more extensive than in earlier mainline entries.

The game is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE. It combines exploration, naval travel, role-playing progression, equipment levels, ability trees, and mercenary systems with the franchise's historical and mythological themes.

Assassin's Creed Origins had already moved the series toward role-playing mechanics, including experience levels and ability development, but it did not offer Odyssey's broad player-directed dialogue system. Valhalla continued and expanded several of these role-playing and choice-based ideas after Odyssey.