Exploring the rest of the ground floor of the mansion:

1) Wherever she finds it, Khessa obviously tries to take as much food and water with her as she can, in anticipation of feeding the reufgees... as well as Seeby! He also urges Song to take it (so that they can take more). Provided of course that it is still edible food! If in doubt, she tastes a very small portion.
If she finds wine, beer or alcoholic beverages, however, she leaves them where they are, explaining: "Even if they were still good, I don't want to risk any of the refugees getting drunk. In the situation we are in, a drunk person would put both himself and everyone else at risk".

2) Wherever they find them, Khessa and Song try to decipher any writings (languages ​​known by at least one of the two: Common, Undercommon, Infernal), at least enough to understand what it is (if interesting, then, maybe they read it completely or take it).

3) In the dining room (the room in the central-southern part) Khessa tries to take the knives with her, in order to arm even the still unarmed refugees (or even to be able to provide a throwing weapon to some refugees).

4) In the hall (the room with the stairs) Khessa tries to take away the curtains (the ones at the far north) hoping that even those can be used either to make bandages or as improvised sheets.

5) In the hunting trophy room (south-east) Khessa tries to take away the bearskin lying on the ground hoping it will serve as a makeshift blanket. Also... is that an armor, the thing close to the bearskin? If so, the blonde warrior examines it to see if it can be used by herself or by Song.

6) From the rooms with beds, Khessa tries to take away blankets and pillows as Clara had asked.

7) In the bathroom Khessa goes into ecstasy at the thought of finally being able to enjoy a proper bath in those beautiful large and spacious tubs... but she sighs and just dreams, for now, realizing that she doesn't have the time. But at least, if there are soaps or bath salts, Khessa takes some! There are?
Also, if the thing in the center of the room is a grate, the blonde warrior tries to figure out where it leads (by looking or letting something fall in).

8) In the closet (the tiny room near the bathroom, on the opposite side of the corridor) Khessa looks for any tools useful for digging (in anticipation of the Ankheg trap).

9) In the kitchen (the room in the central-northern part), in addition to stocking up on food and water as explained in 1), Khessa also looks for any improvised weapons (always for refugees): kitchen knives, butcher cleavers...

10) After that, if nothing interrupted the two intrepid explorers, Khessa leads Song up the stairs, to the upper floor (the stairs go up, I suppose?). If there are no apparent differences between the two ramps, Khessa chooses the innermost one (the westernmost one).

 (@DM: If I wrote a too long post, feel free to reply to only a few points at a time - I know I get carried away sometimes)

[No worries!]

1. Granted -- enough food to not worry for the rest of this part of the story underground.

2. Sadly, just more slavery things -- there is maybe 1 thing of interest which would be a religious text about the duergar patron god Laduguer.

3. Granted -- more can be armed. 

[Son woke up, gimme a moment!]

Oh, ok. Khessa will not take the Laduguer book - Aster seemed to already know something about that god... she does not think terribly useful to deepen the knowledge of that cult right now.

We can resume from 4) at your next time slice!

[I hope all good with your son; have a good night the both of you!]

4.) Granted

5.) The armor is real and it is plate. It is also dwarf-sized. Bearskin rug granted.

6.) Granted.

7.) Soaps are granted. You throw a pebble in that you picked up earlier when you were worried about having to distract the monster earlier. You drop it into the grate. Eventually you hear a splash. Song notes: "Hmm... I think this grate would be hard to pry off without a tool of some kind."

8.) Brooms and mops detected. No sign of a shovel.

9.) Granted and granted. Consider the damage dice of the "Peasant Mob" to be increased since they will all wield knives.

10.) Time to go upstairs? Unless you want to expand on point 7!

5) Khessa looks at the plate, thinking aloud: "I can not possibly fit in this... but you, Song... Do you wish to try the armor? If you can don this, it might protect you better than the one you have..."

The blonde warrior is ready to help her friend try the armor, if she likes to... else, they leave the armor be: 'The plate can be valuable, that's for sure, but it would likely be impractical to carry it through the whole mansion during the exploration'.

7) Khessa replies to Song as she puts a few pieces of soap in her backpack: "I have a crowbar, so I think we could pry it off... but I don't see a good reason to. We got water already and I don't think going down there would bring us nearer to the surface. Don't you get some soap too?" she offers some pieces to her tiefling friend "It could be useful, can't it? You never know when you can meet that 'Prince Charming' you were dreaming of... right?" and winks at her.

10) Upstairs we go!  But when Khessa reaches the upper end of the stairs: "Help me spread this one out, Song, please" and spreads out one of the curtains she has taken with her along this last stretch of stairs, as if it were a carpet covering them.

"It's just a precaution" she explains to her tiefling friend. "If we had to run away in a hurry, chased by someone, after passing this 'carpet', as we descend the stairs, we could suddenly pull it, with a jerk, from under the feet of our pursuers and make them fall".

5.) Song definitely doesn't fit into it. She is small for her kind, but not quite that small!

7.) "Oh my..." Song blushes and eagerly pockets several soaps.

10.) "That's an interesting strategy, Khessa! I didn't know you were such a scamp!" Song giggles.

[I am covering in black some mysterious areas, so feel free to explore the not mysterious areas first. Your movements won't affect what may or may not happen in those mystery areas!]

"Oh, Song, you know..." giggles Khessa too, while she replies "You may never have known my brother Rethos well, because he was so much younger than us... but he has always been a real scamp. I was costantly trying to keep him out of trouble, but I admit that now maybe I'm drawing inspiration from him. After all," the blonde warrior continues more seriously, fixing her blue eyes in those of the tiefling "we are in a situation where I really think I must use every means to get us to the safety of the surface. Not only for me, for you and for the others, of whom I care a lot anyway, believe me; but also for my family. They are still down there, somewhere, slaves to the drow... and slaves they will be for life if I die! I am their only hope," (are her eyes getting a little moistened?) "do you understand, my friend? I, who until not long time ago would not have been able to distinguish a sword from a plow! I wish I was more... more... Ah, but what does it matter" she takes courage, fighting back tears and recriminations. "They have only me. I will try to be enough. Or to improve, if I have the time and the opportunity".

And with that, the tall adventurer begins to explore the first floor with renewed determination.

Now, as far as the 'not mysterious areas' are concerned:

1) In general, I see lots of food and carpets around; Khessa will take them as usual, the food for obvious reasons (you already told we have enough not too worry - but our heroine would for sure take too much rather than too few) and the carpets to improvise blankets.

2) In the initial stairs room there is an armor and a sword? If they are here, they get examined: is the armor of useful size? And the sword is in good conditions? Khessa will not change Cabbage Patch Avenger, of course, but one of the refugees could go better with a sword than with a kichen knife...

In that room I also see something hanging on the wall (there and in the adiacent corridor). Are they paintings? Or mirrors? If they are paintings, Khessa looks at them, curious about what it is painted. if they are mirrors, she would like to take one (maybe it will prove useful in the future) - maybe just the less cumbersome one.

3) In the... what is it? A gambilng all? The room to the east, anyway, I see cards and... tokens? If that's what they are, Khessa takes some card deck (maybe the refugees will have a use for them, once we are back to surface) and the tokens, for she plans to try if Seeby likes to play with them (hitting them, chasing them...). She also takes some firewood, because it might be useful to be able to start a fire and get warm.

There is also a piano? Khessa has no idea of what it is, so she tries to examine it... She soon discovers that hitting the piano keys produces sound and is fascinated by this apparatus... but she realizes that it is too cumbersome to take away (and also that playing for a long time could reveal their presence, if ever there were any creatures still somewhere in the house) then leaves it alone with a resigned sigh: "Really interesting... it's like a mechanical bard, apart from the fact that it can only sing and not play... so it's more like a mute mechanical bard! But, unlike a living bard, it can't even move... and it's too much heavy! We can't take it with us. I'd have loved to have music with us, but for that, we will have to be content with finding a real bard, sooner or later".

4) In the bedroom to the north Khessa takes, as usual, blankets and pillows. I see also what it seems to be a letter? If it is she will try to read it (it might give a clue about the original owner of the house... she is curious).

Then... mystery part time! Khessa will try the north-east part first. She will go to the door, try to listen, then carefully try to open. If the door is locked... oh, well, she will try to improvise a ram with a big piece of furniture and bash it down.

Perception (if needed, when Khessa tries to eavesdrop at the 'door of mystery'): 11

1.) noted!

2.) This armor is actually just decorative, you think it probably wouldn't provide real protection. It is also dwarf-sized anyway. The things hung up Khessa might find are mostly paintings of duergar. She has a feeling she doesn't need to memorize these faces, but she may commit them generally to memory. [No check needed to do that, if in the future she meets a duergar and thinks they might be from here, we will cross the bridge then!] No mirrors present.

3.) Yep! A gambling room. Feel free to add a dice set, playing cards, and similar gaming tools to your inventory. It is also indeed a piano! It's true, I doubt Khessa would have ever seen one. This thing is truly a delightful idea. Perhaps she makes a mental note to find one again once she's out of here.

4.) It is a letter, and in undercommon, it appears to be a simple note about trouble brewing in the tunnels. At the end of the letter, you realize this may have been written right before the ankheg attacked.

Khessa hears and suspects nothing. The door opens easily enough. She walks in through the door and begins to carefully look around to loot like normal. As she begins to inspect the skull on the table [sorry, this is me assuming she would!] she hears fluttering behind her. 

Across the room is a gargoyle of sorts with red eyes that seem to glint ever so slightly. It has a gaping mouth... from which two bat-like creatures emerge! Yet something about them looks like something from a nightmare. They look like the heads of human men, but distorted and melted like an impressionist painting. What is clear to Khessa, however, is that they have fangs and are looking at Khessa and Song like they were snacks!

[roll initiative! Roll for Song as well. Also the picture below is a map, I can zoom out as needed. The bat tokens are hard to see cause they are like tiny creatures, but there are 2 next to that gargoyle in the north. The picture is a link so you can zoom in as necessary!]

Bat Thing 1 17

Bat Thing 2 16

Song: 6

Khessa: 13

Asking in advance: since those things are very small, Khessa thinks an effective way to get rid of them might be to bury them under the bearskin she took from one of the rooms of the ground floor (if caught under the bearskin, the annoyng creatures should not be able to fly anymore... and maybe not even able to come out by themselves, if the bearskin is heavy enough).

What roll should she do to try such a manouver?

(Anyway, the annoying creatures act first - but just to assess whether this is a manouver worth trying or not)

[It would be an improvised ranged attack roll, so like d20 + dex mod. It wouldn't do damage, but it might buy you some time! Or maybe something else depending on what you do.]

/--Initiative--/
17 - Bat 1 & 2
12 - Khessa & Song
/-------------/

The first bat thing swoops in close to Song and lets out a shriek!
Bat 1 --> Shriek, DC 12 Wisdom Saving Throw for both Song and Khessa! [Insight check rolled 1: All you know is this bat is yelling at the top of its lungs and you feel your mind losing its grip.]

[Let me know if you rather me make these saves. Once I see your results, I will continue the combat!]

Oh, well... I don't know which saving throws the hirelings are proficient in, so for the hirelings feel free to roll the ssves yourself. Anyway,  now I'm rolling under the assumption that Song is not proficient in that saving throw (add her proficiency bonus if I'm wrong).

Speaking of the bearskin attack again, could the attack hit both bat at once if they are near one each other? Or only one bat at a time?

Song: 19

Khessa: 12

As the small monstruosity comes near, Khessa just manages to advise her tiefling friend: "Song! Take the bearskin and throw it on them!"

Then, the infernal yell invades the blonde warrior's ears... and, apparently, her mind too! The tall adventurer suddenly feels as though all the worst experiences in her life are pouring out again, all at once, on her!

The darkness... The terror of the complete inability to see... Darkness in which she is touched, beaten, chained...

The memory of her brother Anator, being sadistically gutted by Zrutt, the brutal drow armed with a greatsword...

Her anguish for her family, still a prisoner of the drow, who knows where, but whose moans and vain requests for her help seem to reach her like empathic tentacles...

Her mind is losing its grip.

(@DM: Feel free to go on with bat 2 - just remember to answer to my last bearskin attack question: 'could the attack hit both bat at once if they are near one each other? Or only one bat at a time?' so that I can decide whether it is worth a try or not - at least under the optimistic assumption that Song will be able to act after bat 2!)

[Sorry for my absence! I would let it hit both at once as a bonus for creativity!]

/--Initiative--/
17 - Bat 1 & 2
12 - Khessa & Song
/-------------/

Khessa is completely frightened as the darkness of her own mind engulfs her. So scared, she is stunned. [Note: stunned means you cannot take ACTIONS or REACTIONS. I will let you know when you can act again! For now, please continue your amazing roleplay of her fears.]

Song manages to shake the dark thoughts from her mind. She has lived with fear her whole life... she could endure this!

The second creature swoops towards Khessa, making a vicious attack!
Bat 2 -> Khessa, with ADVANTAGE due to STUNNED (Attack: 16 Damage: 5 + 4 poison damage. Poison damage cannot crit.)

[Song may take her turn! Khessa is currently unable to grip reality.]

[Thanks for the bonus, Khessa and Song will do their best to get to survive yet another time!]

Song follows the advice of her scamp friend: she grabs the bearskin Khessa had kept as improvised blanket and tries to bury the two dangerous (but very small) monsters under it.

The second bat thing manages to come near Khessa and tries to bite her! The stunned blonde warrior seems an easy target, but Song's actions distract the monster enough for it to miss.

Just a moment later, the bearskin comes down on the both of the annoying flying pests...

Bearskin attack: 7

[WAY TO GO SONG! I'LL KISS YOU AS SOON AS I AM ABLE TO!]