Burnt Offerings -Reason to explore the ruins of wrath

[Toshy]

So, I'm about to run RotRL Anniversary Edition and read through the first book Burnt Offerings.

So far so good,but one thing in particular got me wondering:

What would be the reason/motivation for the players to actually explore the ruins of wrath?
If didn't miss anything the ruins are only vaguely mentioned in tsutos journal.
Knowing my players it would seem way more reasonable to ignore the catacombs and move on planning to take on thistletop.
Especially if they manage to coerce tsuto into giving out information via magic and therefor knowing about nualias plan and everything on thistletop.

Ignoring the catacombs would skip valuable parts of information, loot and especially experience and they might get problems at thistletop beeing underleveld.

Did I miss anything? If not what hints or other forms of motivation could I drop to make delving in the ruins seem more attractive or necessary for them?

[Bjørn Røyrvik]

Why? It exists.
Honestly, if the PCs aren't interested in exploring newly uncovered ruins for some sort of reward (usually monetary but possibly moral or academic) they shouldn't be PCs. Sure, they may want to do Thistletop first but that shouldn't be an issue.

Less snarky metagamey, the PCs could investigate to make sure there aren't more goblins hiding out in there. Maybe Tsuto could say something to the effect that he was unsure how many goblins there were with him and there may be some in the Catacombs.

On a general note, when it comes to APs, several of us have found out that milestone levelling is the best way to go. Many encounters are just there to hand out xp and often get in the way of engaging with the story. As long as the players engage in story points in the right order, just letting them level when they are finished with one chapter is a lot easier.

[Toshy]

That players should explore, because that's what they're supposed to to is clear to me.

What I'm asking is, if there is any reason for the characters story wise that I might have missed or overlooked?
As far as I have grasped it, there are only very vague hints that the ruins pose danger, whereas thistletop is where all the problems with the goblins seem to come from, so it seems way more likely for the characters (who want to aid sandpoint) to let the ruins be ruins and head directly to thistletop.

[Bjørn Røyrvik]

To expand on what I said earlier, if the PCs have Tsuto they have most likely gone to the glassworks, which IIRC leads to the top floor of the Catacombs. It's not a stretch to expect the PCs to check it out in case there are more nasties waiting in the shadows, especially if you tell them that they hear some strange sounds coming from the tunnel.

Perhaps Tsuto himself, either in person or in a journal, mentions the existence of the catacombs to entice the players. A gentle GM nudge like "So you want to head out to Thistletop which is a ways away and leave this very convenient and very mysterious tunnel that is RIGHT HERE until later, right?"

Here are some other ideas

And, if you use milestone levelling you don't have to worry about them being underleveled if they skip past certain encounters to get to the plot-relevant points.

[Aristophoenix]

No, you haven't missed anything explicitly pointing the PCs to the Catacombs. It was intentionally written to be a bit flexible to adjust for party actions.

Both times I've run RotRl, Tsuto escaped the glassworks encounter via the smugglers' tunnels, and the PCs stumbled upon the Catacombs of Wrath attempting to follow him. They realized pretty quickly that Tsuto had not gone that way, but were curious enough that they explored the Catacombs anyways. Considering as-written Tsuto is passed out drunk when the PCs run into the goblins in the glassworks and Tsuto flees down the tunnels if his goblin minions are defeated, I'd say that outcome is likely for most parties, so your problem will probably solve itself.

However, the RotRl Anniversary Edition mentions that the PCs might not find the Catacombs before going to Thistletop. Leveling-wise, I agree with Bjørn that in general for APs milestone leveling works better than XP. If you're using XP, I'd throw a few appropriate encounters in en route to Thistletop to give them a bit of a boost. Make sure they run into the emaciated Birdcruncher goblins in the thistle maze for an easy XP boost. (A curious goblin could go to investigate the sounds of movement...maybe it's something they can eat!) But honestly it's been my experience that most of the encounters in Thistletop are fairly easy for the recommended level, so even if your PCs are half a level or so behind, the should be able to manage. Maybe take extra care not to have the goblins in the fort swarm the party if you don't think they can handle it, but if you take it room by room, they should be fine.

In terms of missing information from the Catacombs of Wrath and dealing with the threat Erylium and the Sinspawn present, if your PCs end up dealing with Thistletop first, Nualia's journals have extensive details on the Catacombs, the quasit, and the runewell. Finding out a demon is summoning monsters beneath Sandpoint should be plenty of motivation for the PCs to investigate. And if the PCs somehow miss Nualia’s journals pointing them in that direction, eventually Erylium should grow bold enough to start sending sinspawn to the surface, and the PCs can get involved that way.