During its E3 2019 pre-show, Ubisoft dropped a big surprise: The Assassin's Creed Odyssey Story Creator, a free set of tools for Odyssey that allow players to write and script their own quests. The tool set is accessible from the official Odyssey website and is free for anyone to use, even if you don't own the game. Also, it's out today.
Ubisoft said that Story Creator is based on the tools the team uses to create quests for Assassin's Creed, and it seems pretty powerful. You can write branching dialogue trees, import any character model from the game, design combat encounters, and chain multiple quests into one larger story.
You can publish your story creations to the online hub for others to import into their game on all platforms. There's already a bundle of 14 quests live for folk to try out. The user manual for Story Creator is a whopping 157 pages, so it'll be interesting to see what people create as they get acquainted with the tools.