WARNING SPOILERS!!!!!!!!!!!!!!!
I love this module. There were things that jumped out when I ran it, that I didn't even think of when I just read it. I didn't realized that almost everyone offers the party wine, and the party starts to get real suspicious of the wine.
The first person they meet is the local sheriff. Make sure to play him as nosy and questioning. It actually makes the party respect him for doing his job. Little do they know....
It can trigger later if they ever think to turn someone in or go to the law for help, they go right to him. And then he can go "Ah, let's go get some help... at the temple"
The crazy blacksmith is one of the greatest NPC's ever. Play him for maximum aggression to pick a fight, make him like a barely contained rabid dog, it's often the best place for the first fight to break out. As you ask for initiative, Your players will be like "what are we really going to fight this guy?" "He's a townsperson for crissake". Then his wife and kids get in on the fight. She has a crossbow I think. It's awesome.
I ran this in 4E, where its super easy to just knock people out. So I made it so that any charmed person (cult member) when they got reduced to 0 HP, would start gurgling green bile, and die even if someone tried to knock them out. It ensured a body count. Kept the party from easily interrogating someone, although the cult members are charmed, so you could instead, rule they resist interrogation.
Also there's two inns in town. Their names are somewhat innocuous. something like Honey, and the other is Slumbering Serpent something or other. I didn't even realize that when the players start getting suspicious and desperately need somewhere to rest, they will avoid the serpent simply because of the name, snake~reptile? metagame with the title? Oh and dont let them rest in the streets or in townsperson's house, remember all the town are suspicious. Even if they do somehow convince a townsperson to let them rest in their home, you can do the ambush scene there.
Oh it's such great glory if you can get them to go to the honey tavern. The little rat faced guy cooks their food, and he can put sleep poison in it. If that happens, just launch the ambush right then and there. If half of them fell asleep, let the others wake them with slaps or something. After a long day, a big feast somehow puts even the most suspicious adventurer at ease.
It can be really cool if Derek, towards the end of the fight, says "Hey, I know what's going on here. I can help you. I can tell you where the cult is" There's a very slim chance you can get the party not to kill him, and even slimmer if you can get the party to allow him to guide them. But if you do! there's so much potential for future betrayal!!
The ambush scene. You have to flexible. You don't have to force it to be in the rooms of the inn. You can have it happen anywhere in town, or even in the woods, if the party is so paranoid they sleep in the woods! Do it at night when they are damaged and out of spells. Try to control your dice so you dont kill the party, it can get dangerous. Or even if you have a TPK; you can always have the classic "whole party is tied up and left alone in a room while the idiot minions go notify the big bad guy" and of course the party gets an attempt to escape. Always a fun scene.
My players were like "this town is crazy, surely the temple might be able to help us." ha ha ha
The temple is like another perfect place to launch a betrayal/ambush. With a cleric, and several monks it can be a really cool fight.
The very scared townsfolk are actually nicely detailed out. Each one has a description of what they do when approached. Enough that you can make more up on the fly as to their motivations and personalities.
Ramne who is often assumed to be with them, comes with Dispel Magic. Very useful for dispelling Charm Person. If he's not with them, maybe consider having some scrolls of dispel magic.
Don't be afraid for the Naga to open up with a Fireball (which is part of the classic memory for this module). I just ran Starter Set and a 4th level party can take a Fireball, they took one from the Flameskull. As long as someone has a healing potion to get a potential downed healer back up. Actually opening with the fireball is over-all much safer than saving it for later when everyone is bruised battered.
Plus always keep in mind. The naga is arrogant as all hell, so if there is ever a TPK, remember she puts all the players in a room, and will try to seduce/charm each one in turn. She wants more cult members, and isn't ever worried about being defeated. She is immortal after all. Doing this, allows a reset, and always keeps the story going.
