Sakkara and Time

I hope this is the best forum for this question...

I'm running a sandbox game in my own setting and I have placed Turos and the caves with the Sakkara stone near the starting location.

My players' first party started to explore the caves before they got stupid and died.  

Their subsequent parties have passed through Turos on the way to a city (multiple times), but have never ventured to the caves (they instead found the dungeon of Stonehell on the map and have been living pretty exclusively for that).

But the story of the Sakkara stone has been "activated," as it were, by the previous party's incursions.  Forgive the video game terminology, but it seems apt for a sandbox game that certain plots don't "start" until the players engage them in some way.  Such is the case with Sakkara, which has a corrupting influence on the area.  

It has now been about 6 months in-game since that previous party went in there.  I'm curious how I should handle this.  I have mentioned that sightings of more and more fierce beast-men in the mountains along the highway have been spotted.  But I know that the chaos corruption should also be affecting the residents of Turos,

I could simply have the fortress fall to the beast-men, but knowing the way players operate, when you throw out a big detail like that, players often take it and assume, "this is what we're 'supposed' to do now."  But we're all having fun in Stonehell and I don't want to deprive the group of that.

The easiest answer, of course, is to just ignore the corruption entirely.  But I'd like to find a compromise position that still lets them know there is evil afoot, but not one that seems to demand an immediate and lengthy in-game response from the players.

Any thoughts, wise ones?

You could tell them that another party defeated it, but at great cost.  Maybe Turos Tem was devastated before a band of heroes defeated the empowered denizens.

Hm.

I think Turos Tem might just be on the edge of the coverage; I think the max was a 24 mile hex, and TT is either half-covered or right next to the 24m hex that would be centered on the mound.

In either case - if the taint doesn't reach fully, and it's more  the more mundane effects could be held at bay if Valerian was able to persuade whomever exists in your world to fill up the garrison - if they're mostly occupied keeping the trade lines open along the river and into Siadanos, there may be enough built-in delay before it all goes to heck in which the PCs could still react. May be worth looking into the mercenary recruitment timelines and see what it would technically take for Zakiti to build up a sufficient force.

But that level of activity, where they're suddenly seeing double-guarded caravans and perhaps they're getting hassled by The Man trying to figure out if they're part of banditry or not may slowly get their attention.

And the problem would be bigger, and they'd be at a higher level to deal with it.

Thanks, everyone.  They happened to be traveling through Turos and I told them that another party was on its way to deal with some sort of evil artifact, but never returned.  That motivated the PCs.  They went to the 2nd level straight away through the spiral staircase in the bandit area that leads to the ghouls.  That also provides a pretty straight shot to the BBEG (which I didn't realize when I sent them that way, but it worked out).  Epic combat followed; the heroes prevailed, but at a cost.

So they made it out, but now they're reasonably wondering: what else is in there that we missed? Herein lies my new problem for which I am seeking advice:

Treating the remainder of the place like a traditional "dungeon" at this point seems foolish, as most of the disparate groups were there because of the stone and the Lady Below.  But I don't want to waste my players' time by having them search through a bunch of empty rooms.  There will likely be several days bstween the Lady's defeat and their return to the cave, so that's ample time for the denizens to get out of Dodge.

Any ideas about how I could handle this situation? Thanks in advance.

option 1) telegraph that the dungeon is useless now and have signs that the previous denizens were slaughtered in the ensuing chaos.  If they press on, maybe give them a small parcel of treasure defend by a few secretive holdouts.

option 2) repopulate the dungeon! now there's a power vacuum in this handy, mostly empty, and easily defensible area.