Lazybones
Adventurer
1. If a character with a Passive Perception equal to or higher than the DC approached close enough to the door to notice any signs (e.g., scrape marks on the floor, a slight gap in the blocks of the wall), I would give them a hint. Otherwise they have to make an active check to find secret doors.In an effort to understand D&D better (I have only ever been a player in a long-term homebrew 5E campaign), I started reading Quests from the Infinite Staircase and the 2024 DMG.
For Infinite Staircase, I've gotten through the first module, The Lost City, and I have a few questions.
2. If the party is using a light source (remember that using only Darkvision applies Disadvantage to Perception checks), the stirges should wake and attack immediately. I would be fine giving them surprise, especially since Surprise isn't as big a deal in 2024 as it was in the 2014 rules. If a) no character with a light source was standing close to the door when it was opened, and b) a character said they were looking around after hearing the room description, I would have them automatically notice the stirges since they aren't really "hiding" per se. But if they just waltzed on in holding a torch or making noise, it would be time for Initiative.
3. I will often add a bit of miscellaneous description to "empty" rooms for flavor, your idea is a good one.
4. There's no way I'd use the encounter provided with a low-level party. As you note the adventure indicates that the level holding Zargon is completely optional, and should probably only be used if the DM has fleshed out the underground city with sufficient content to bring the party up to a reasonable level, or if they are able to leave the pyramid and return once they have gained sufficient experience to be able to handle a CR17 opponent. I don't particularly like the idea of a far superior monster tormenting player characters that don't really have any chance of beating it.