An End of Act is triggered whenever either the Player Discovery token or Enemy Discovery token reaches a specific position on the Discovery Track. Act II starts when position 4 is reached, Act III starts when position 8 is reached, and Act IV starts when position 12 is reached. An Act only starts once, so if one token reaches the start position after another token has already reached it, no new Act is triggered.
At the end of an Act, the following things happen, in this order:
1. If the Player Discovery token was first to reach the position that triggered the End of Act, each player gets to collect a new Order token of their choice; either one of the standard ones: Crew Order token, Navigation Order token or Artillery Order token; or a Fleeting Order token, which works as a single-use wildcard order.
2. If the Enemy Discovery token was first to reach the position that triggered the End of Act, advance the Elder One Discovery token downward (towards lower numbers) on the Discovery Track, one step for each step that the Enemy Discovery token is ahead of the Player Discovery token on the Discovery Track.
3. Move the token that wasn't first to reach the position that triggered the End of Act to the same position as the token that was first.
4. All players have to pay wages to their Crew members. The wage due for each Crew member is equal to the original recruitment cost (marked on a coin icon on the Crew member's Crew Board). If they can't or won't pay for a Crew member, that Crew member leaves (shuffle its Crew Board back into the Crew Board stack next to the Game Board).
5. Place each cards below the Ongoing Stories cover card facedown and perpendicular (turned sideways) on the deck that has the same type of cards (same backside art). (Placing the card perpendicular is done in order to make it easier for players to remember that it's a part of an Ongoing Story, and thus needs to be cross referenced against the card that triggered it.)
6. Spawn a Storm tile with a size equal to the new Act number.
7. Spawn an Enemy Ship on a randomly chosen Enemy Ship Spawn space (hex spaces on the Game Board with the red enemy icon).
8. Shuffle the stack of Enemy cards that belong to the new Act into the Enemy card deck. Note: the core game doesn't have any new enemy cards for Act IV.
Unclear detail: if the new Act is triggered by something other than the regular Discovery Track advacenement during the Enemy Phase, the rules are not entirely clear as to what happens next; does a new Round begin right away, or does the End of Act events only temporarily interrupt the on-going Round which then resumes?