It seems some features/changes lend themselves to user stories: "as a user, I want to be prompted to exit or retry the battle after the hero dies, since these are the only two common navigations". But other features wouldn't be a good fit for stories, like a detailed description of which game elements appear during an event.
How are these detailed specs incorporated into the agile task system? Certainly the umbrella task could be written as an epic, but the specs seem not to fit as stories. (They are not about direct user motivation or benefit, because these specs often make the game harder, like "boss health should refill at 100% per 90 seconds".)
Note: we're using Jira to track bugs and tasks.