Lost Halls of Everforge

Hey there, just a few questions about the Lost Halls of Everforge module 1) When do you roll on the random encounter deck? I assume once per room except for the initial hall but it isn't mentioned anywhere. 2) What does "On initiative count 20 (losing initiative ties)" mean? I again assume once you reach round 20 then the dragon starts to use lair actions. I have never been in a combat that lasted quite that long so i am not sure if that is a typo or not. A couple of quibbles; the patrol groups are rather large. So large i am wondering how they will all fit in a single room together. Also it seems strange that the patrol deck idea can be made completely redundant by the party just marching straight ahead into the main and final encounter. The idea is really cool and has introduced me to a cool way to do random encounters (the cards) but it is just a little confusing as written. Thanks heaps for any help or a pointer in the right direction.

I can answer 2) -- It's common for lair actions to go on a particular initiative count, but every other creature that got that initiative goes first on that count.  You can think of it as happening after initiative count 20 but before initiative count 19 (trailing edge activation, if you'll pardon the computer science term.. =D ).

Thanks mate. Clearly i haven't run a campaign long enough to encounter one of these creatures yet.

No problem.  I would guess that your assumption about 1) is correct.  I know that's the way Curse of Strahd is set up.   I've not looked at the encounter groups, but if there are two many for the room in question, you could draw again, or stagger them (half the encounter is in the room, the other half approach from either the way the party came from or another hall or entrance), or discard half of them and make the remainder twice as hard. =D