My players just finished the Boiler Room encounter in Bordrin's watch...
I'm curious: What's stopping them from going straight the Nexus next? What incentive do they have to go to the Living Quarters or the Shrine? I'm sure I can make one up (Nexus is locked, they need a key), but the module doesn't seem to give a reason for them to go there.
Btw, the Dark One in the boiler room was a bad-ass. :D
To the north 60' away are orcs and a troll around the corner eating! Kinda hard to miss.
To the south 80' away is an open door that has light coming from it along with sounds of 7 orcs searching.
Both groups do not have darkvision (choker being the exception) so they need light that is easily visible. If the party is silly enough to bypass the fight then when they start making noise in the Nexus the two groups should join in, try to have Kalad suggest that might be the result, if he is with them. They should feel inclined to take them out now so they aren't at their backs later. Being able to take the groups out in small groups is just a sound tactical decision.
Plus after a few encounters like that off the beaten path that hold treasure they will find it's in their best interests.
Any religious ties from the characters that could be used to encourage them? Dwarven possibly? Hard to give other suggestions without knowing more about your party makeup.
I think if you go with the monster placement per the module, aren't there orc in the hall towards the shrine? They would surely attack if the PCs did not attack first.
I don't think so. I know if the Dark One Emissary is able to escape the boiler room (he wasn't able to), he runs towards the shrine, persumably leading the party there.
I do like the idea of the orcs making enough noise to be heard, since they aren't really that far off.
I think Kalad's a very useful tool here. I had him suggest to the party that the other places should be checked first, just to be sure there's no other orcs within the cavern system. The Nexus is a hard encounter, mostly because it's not a straight-up fight. My party of six made it out, but only after using everything they had, coming fresh off an extended rest.
If Kalad didn't survive the encounter in the Monastery, then you might want to have the party hear the orcs in the other two rooms past the Boiler Room (what was it, the Shrine to Moradin and the Barracks?). Those encounters should be enough to make them want to take an extended rest after the other three fights, and that'll leave them ready to take on the Nexus at full strength.
Good luck running the encounter, it's a blast!
Granted, my group is currently a party of only 4 + Kalad, so perhaps I should allow them to take an extended rest before the final battle. Especially since I haven't been lessening the difficulty of the encounters.
Regarding the original question: the monsters in the shrine area should be detectable from the main hallway. There's no door and a large cave troll present, so the heroes should probably hear something and see a light-source. My players may have missed the other room though (it's been a year so I'm trying to remember the details...) but it's not that important.