Any time you see a pop-up screen when you're about to venture forth, that's pretty much the next act.;
- ACT 1 - Everything between the Prologue and Grymforge
- ACT 1.5 - Mountain Pass
- ACT 2 - Shadowlands
I heard you can do Mountain Pass after Shadowlands as long as you don’t hit the point of no return. I really wish Larian had committed to Mountain Pass being either Act 1 or Act 2, as it currently sits in a very awkward spot in the game’s progression. I think of it as Act 1, and part of why Acts 1 and 3 are vastly superior to 2, but others think of it as Act 2, and a redeeming factor therein.
