Thank you! 🐭 Honestly, it's a bit of both, but mostly the road there.
The ending itself is decided on one big night near the end of the campaign. But which choices you even get that night depends on how you handled things along the way: whether certain factions trust you, who you made peace with instead of fighting, what you found and kept to yourself. Burn a bridge early and that ending simply isn't on the table anymore. A couple of endings are always possible; the others you have to earn.
How you resolve conflicts also pushes the factions' own plans forward or back, so the world you arrive at on that last night looks different depending on how you played.
The demo is only the prologue, so none of that is in it yet. The full game, with three acts and five endings, is still in the works. Thanks for asking, that's exactly the kind of thing I love talking about!