Heading back to the camp he says, "Sir, I've found a cave which would be good for us to set up a base for now, at least until I can get some tools to work with the wood here." And looking to their new miner companions adds, "the cave may also lead deeper, though I know little of rock. I'll leave that to you." Then to the group as a whole, "I believe we should fill our waterskins, perhaps grab a handful of any fruit you may see from here, and head to the cave to rest until the morning to begin our work."

“Thank you Duncan, that sounds perfect.  Let’s make our camp there.”  Kas ritually casts unseen servant to give additional help with carrying things over, water, fruit, any firewood, etc and they begin to make a temporary home out of the cave.  

Everyone moves to the cave and settles down as it gets hotter

(I assume everyone will rest until late afternoon)

Now its late afternoon what do you do?

(Is this a long rest?)

(Yes)

Though he hasn't got the proper tools, not having been aware that the land was this barren, Duncan will make do with what he has. Fortunately, he's collected some weapons from the raiders and assassins, and while swords don't make the best axes, it's better than dulling his own blade, so will use them to begin to collect branches from some of the trees to work on crafting a sort of lean-to in the cave, hoping to create a shelter that, at least from a distance, appears as little more than a natural group of plants near the cave entrance, so that they do not need to worry about prying eyes. While doing so, or after once he sets down for a rest, he'll then go the top of the cave and set up a small watch post for himself, where he'll be able to, again, stay somewhat unseen, yet able to see anyone who might approach.

Ellesia scans the land from the cave "Now where to start. If you have emeralds where would it be." She then leaves the cave "I am going to need to do a thorough survey of the this land" she then heads out with her tools.

"I'll go with you Ellesia" says Willoughby

Duncan as you build you notice off in the distance some stones with chisel marks.

Knowing little of stone work, Duncan would call over Ellesia and Willoughby, who seem to be more knowledgable in this area, and show them them marks during a bit of down time, and ask them what might have made this type of mark, and if they mean anything, as well as if they have any idea on when they may have been made (ie not too long ago, 10+ years ago, ancient...). Duncan would then of course share this with the others.

Ellesia and Willoughby look over the stones and the surrounding area.

"Its not ancient and I think there is something underneath I believe it was built within the last decade." says Ellesia

Willoughby touches the tool markings "There is magic hear. I can sense it. An Arcane Lock. It needs the correct passphrase to activate"

Duncan calls out "Kas! Hrath! Get your magic butts up here! Something you should see!" and shows them the markings explaining what the others just told him.

Hrathen looks over the stones then shrugs. "I don't know the required magic to open this lock, I'm afraid. That said, I do know it would be very, very difficult to open. If anyone tries, let me know. I can cast a spell that could aid them." (If anyone tries to pick the lock, Hrathen casts enhance ability on them, giving them advantage on dex checks for an hour and protection from fall damage of twenty feet or less.) Hrathen will then cast detect magic, searching for any other magic in the area. Investigation: 19

Hrathen detects transmutation magic among the stones.

Kasbis is interested in the finding, comes sauntering over with his backpack and pulls out an old musty tome.  (Pact of the Tome).  He starts reading and ritually casts identify to try to help their investigation of this rock and what might lie beneath, in hopes to know their next step.  “I’ll try to learn what I can about it, but I might not be able to undo that lock…”

Kasbis identifies the arcane lock and that the rocks are magically bonded together. You can surmise they were once part of some kind of structure. Using the correct passphrase or lock picking the lock will reactivate the magic dormant in the stones. Once activated the stones would reconfigure to rebuild the structure via transmutation magic.

Your not sure what is underneath the stones

Willougby opens his bags and provides some small tools that can be used for lock picking. "Here try using my clock makers tools"

"Is there anything your father said that might be a clue to the phrase needed?" Duncan says, trying to help the knight think reminding him of the time he met the late lord.

(For this Kasbis can decide what the passphrase is. It would be something only he knows and was only shared with his father)

Kasbis stands up straight as a rod, a bolt of inspiration has hit him.  He pieces together conversations with his father, things that he overheard, conversations that he wasn’t meant to hear.  A few (too few…) real talks with his father, discussion of family affairs, the future.  “I have it.” he says out loud.  

“Menzora tetrehue, zildoflue, seb saphet xerosis.”  Words in Abyssal come out of Kasbis, toward the rock formation.  He watches to see if he is right.  

“One of my father’s favorite sayings.  Work hard, study and crush your enemies, family first.  The last part is laughable.”

The stone slabs float up and assemble this stone hut with a closed stone door.

“Well this will save some time,” Duncan says, quite relieved that maybe he wont need to actually build a full shelter out here, though also a bit worried that he’ll need to memorize that strange phrase to open it each time. He then lights a torch and pushes the door open, peering inside, ready to explore.