when does act 1 end bg3

Act 1 in Baldur's Gate 3 officially ends when the player leaves the Underdark or the Mountain Pass and enters the Shadow-Cursed Lands. At this point, a message prompt appears warning that the adventure is progressing to the next act, and the player is asked to confirm if they're ready to advance. Once confirmed, Act 1 ends and Act 2 begins. This transition typically involves taking an elevator from the Underdark or going through the Mountain Pass gate, leading to the new area called Moonrise Towers or the Shadow-Cursed Lands. After this, players cannot return to Act 1 areas, marking it as a point of no return in the story progression.