Hey, my players don't read this. If you don't think you are my players then be warned that this is filled with spoilers.
So I talked to some friends and read some ideas on here.
So at night it started raining and the fog rolled in. In the middle of the night(when most of them were asleep) they started hearing baying from Yeth Hounds. Since all three Yeth hounds were baying at the same time I increased the DC by +2 for each additional hound for a total DC of 16(upon further reading I sould have made my players roll three times since).
Whether or not the save is successful, an affected creature is immune to the same hound's bay for 24 hours.
Nearly all of my players ran except the witch. As they were running back they came across two Yeth Hounds. I was intending to scare them away so that the goblins could build a simple bridge and my players would give up their idea of starving the goblins.
Because I use macros(roll in front of my players) I couldn't(cheat) stop one of my players from dying from a Yeth Hound bite when she tried to stand up after being knocked prone. That player was incidentally my mother. I kill her the day before mothers day! :(
After that I had the Yeth hounds run away. They did what they were told to do and they didn't want to press they're luck. (Also more players would have died.)
My players did eventually run away, but they seem to be convinced that they have defeated the goblins because the goblins couldn't possibly make a new bridge quickly enough to stop them from starving.
They went around kill off the remaining goblin tribes. I tried to emphasis that the other tribes are mostly pregnant females and children.
I don't want to punish players for thinking outside the box, but I'm not convinced the goblins will starve. A simple rope bridge wouldn't be too hard for the goblins and their friends to make. Especially since they have had to fix it before.
Originally, the goblins rigged the bridge so that it
would fall completely into the water below, but when they
tested it and realized that they’d stranded themselves on
the island, they rebuilt the bridge so it would leave one
rope connected, making it easier to repair.
My players are also now convinced that the monsters in Thistletop are impossibly hard to kill. I tried to emphasis that the fight with the Yeth Hounds was especially hard because they were taken by surprise(split up and without weapons).
My players seem to think letting the Goblins try to raid Sandpoint is a better plan because they will have the help of the people in Sandpoint.
I figure that should be a very very hard fight.
Here are a few points you might want to share with your players via direct DM feed, NPC's, knowledge checks, etc.
The goblins are really good at scavenging. The entire fort appears to be made of scraps from other buildings, etc. No matter what condition the players left the previous bridge in, including complete destruction/burnt to ashes, the goblins probably have the parts to build another one.
The yeth hounds can fly. They don't need no stinkin' bridge. That's how they attacked the pc's in the first place. The yeth hounds will be able to ferry goblins, materials etc. from the island to the mainland. A new bridge is therefore just a matter of time. The only way to stop that is by holding the mainland in force. You can't lay a siege if you don't surround the castle.
Anyone in the party have Knowledge: the Planes? Check the spread area on the hound's Bay- it's 300 feet. If there is an attack on Sandpoint and the hounds are involved, it's all over but the crying. That fear effect is going to turn any battle into a panicked rout. The citizens and even the town guards are not going to make those saves in enough numbers to fight off the goblins, hounds, Nualia and whatever the heck Malfeshnekor is.
I assume Hemlock has not returned from Magnimar. Maybe if he was in town with some soldiers, they might be able to fight off the goblins - but casualties will be high. All in all, no one in town is going to favor fighting the goblins in Sandpoint over fighting the goblins and their allies anywhere else. I would think the position of the Mayor and other VIPs would be: you kicked the hornet's nest, go deal with it before they follow you here. Of course that doesn't mean various NPC's in town will not volunteer to join the PC's in an assault on Thistletop. A pitched battle between all of Thistletop's residents vs the pc's and a half-dozen leveled NPC's from Sandpoint might be pretty cool. Candidates might include Shalelu, Zantus, Hemlock, Ameiko, Daviran Hosk, and Ilsoari. Of course you have to stat up and run all those NPC's since the AP doesn't provide that info...
I make it clear to my players: if you have a clever, legitimate, or fun idea and it makes more work for me, that's my problem. If, however you are lazy or chicken and it makes more work for me, I turn the "player-suffering dial" to 11. You might for instance remind the pc's that treasure and experience will be divided between all the participants. If the town is going to take a lion-share of the damage from an attack, take a lion-share of the risk, etc. then they are going to get a lion-share of the loot and xp (assuming victory.)