(My head cannon the voice is more like Jack Sparrow, but have him have what ever voice you want him to have.)

As the sun is coming down you come across the ruins of an ancient Oahtu outpost, abandoned long before the current troubles. Its coconut shell doors have rotted away, and the walls of packed earth have begun to crumble.

You enter the building to see if it would be a safe place to sleep for the night, the first chamber is about 30 foot round, with an extra more squared off area at the far end of the chamber.  In the center of the room is a 10 foot circle, it was once a pool that has dried up, there is a little bit of water in the pool that emits a soft luminescence.

Off of this main chamber one each side of the squarish outcrop is a doorway (2 doors in total). The doorway on the left, the coconut door is also rotted away you hear chorus of soft chirps.  The doorway on the right you can tell was thicker because there is more rotted shell, and there is even some still left on the hinge, there is no noises coming from this room.

The little light that is left as the sun is setting is enough that you can see in the main chamber but not into the two side ones.

What do you do?

Kraven I started to type, pause to teach students, then finished and posted and didn't see your post. That being said you go from being sure you are being followed to knowing your not, back and forth.

"You know this place, Mr. One?" Mist asks. "Seems a bit creepy to me. Kraven, maybe you could check out whatever's making that chirping sound. Bigm'n and I'll be right behind you. Dru...ever seen water glow like that?"

Arcana or investigation: 18 (or subtract 2 from that for nature) to try to figure out why the water's glowing

Kraven nods his head and then whispers to the group, "Not sure but I think we were followed here, careful." Then Kraven will sneak up to the door and listen in and then peek inside.

Stealth: 28

Perception: 12

Can Mist help Kraven perceive the room but peeking under his wing?

I'm going to say no to the advantage, mostly because the check is strong enough as is.  

Mist you dip your finger into the pool, then lick the water off it.  And you notice 2 things, first you start to get the same feeling you would get when drinking a healing potion, second your fever starts to go down a little, but neither feeling stays for very long.  Roll a D4.

Kraven, you sneak into the chamber, and you see the sorce of the noise, you make out a nest, sitting o. Top of the nest is an iguana, she is bent in an odd way most of her body is in a u shape and her head is cooked back to look at the door way.  Behind her body you can make out some movement, and then you finally see it, babies.

@Druquilla

" Magnus doesn't know much about this. But as we all have seen before… The fragments of the fallen star did a lot of strange stuff before. So I wouldn't be surprised if it made plants super intelligent and ambitious." 

@Mist

Gintarou tried to pass some of his weapons to the fell one. But he stops when he hears about the man's story. " Yep. We met quite a few interesting people during our voyage. But I'm sure who we are going to meet in the future. They will be I-gonna-bite-your-head-one and planting-my-seed-in-your-brain-one. By the way… " The warrior pretends to pick up an axe that he drops on the ground and whispers to Mist. " … Did you remember what the Elf said? There were who looked normal then eventually started to attack others. That's part bothers me… " He eyes the fell one. " … A lot." 

Gintarou decides to clear the building as soon as they arrives Oahtu outpost. " You may call me worrywart. But I can't sleep well in a place where I don't know much. " Using his polearm, the warrior pushes open the right side door ( or the remains of the door ) and peeks inside. 

Perception: 18

Also if someone jumps on him, they will provoke Opportunity Attack from Polearm Master

Bladed Oar Glaive: Attack: 9 Damage: 13

The right room, are heaps of rotted and broken furnishings, but one thing appears intact: a coconut wood trunk. Remarkably, it's still sealed and locked.  No creatures or or beings in the right.

Kraven moves back to the group and explains what he sees, and that we should probably just ignore that room otherwise we will have to deal with a rather angry mother lizard. Then he will sneak into the room with the chest and see if it is locked or trapped. Then will try and open it.

Stealth: 27

Perception: 13

Pick Locks: 10

Kraven you do not notice that the chest is trapped, while you succefully pick the lock a needle pops out and pokes you, take 15 poison damage, and make a DC 15 con save or be poisoned for the next hour.

Quote from coachmanak >>

Roll a D4. 

d4: 4

"ACK!" Mist cries as he sees Kraven's hand get skewered. "Come in here and dip your hand in the magical healin' pool. Guaranteed to cure what ails ya!"

If Kraven hasn't already, Mist will use the tip of a dagger and carefully lift the chest's lid the rest of the way to see what's inside.

Also, can we see the bottom of the pool?

Yes, groud is at the bottom, however Mist what you do figure out is that you could use the water from the pool as a potion of healing, you can make 3 of them.

Inside the chest you find a pearl chip worth 50 GP.  And 

Coconut Shell Shield. A triangular shard of coconut shell designed as a shield. An abstract glyph resembling ocean waves is carved into its face. Light and maneuverable. 

Carved Husk Art. A piece of coconut, small enough to fit in the palm of one's hand (even at insect scale). It's been intricately carved with glyphs that vaguely resemble things from the natural world, such as trees or insects.

(Do we have anything we can put potions in?? Can we glaze over that bit?)

"Don't fancy sleepin' 'ere with these legged snakes," Mist muses. "Bigm'n! Think you can set up what's left o' that door over in this room so we don't get eaten tonight?"

@DM, you said the iguana is in a weird position. Does it seem unnatural in any way or is it just usual iguana stuff that we're not used to?

It's using its body as a shield for her babies from what ever might come into the door and looking at the door to see if anything comes in.

At Mist's question about seeing water glowing Druquilla thinks for a moment, "An animal could cause the water to glow but aside from that I do not know of anything off the top of my head."

"What are you think..." Druquilla starts shouting when Mist touches the water but stops when she sees it had a healing effect. "You are lucky that didn't poison you further." 

"If we are going to spend the night here, we should figure out a watch rotation, I can take first watch, but I do agree we should be careful of the lizard in the other room."

Kraven Con Save: 9

 Kraven yanks his feathered hand back and then almost immediately feels woozy as he sinks to the ground. "Thought I had it but stupid trap. Rest here for the night right?"

@Kraven

" Oh! Crap! You okay, Kraven! " Gintarou drags the rogue back to the healing pool and treats his wound. " … Paranoid idiots! Why did they set traps in their own house! "  

@Mist

" Well… that lizard mom only wants to protect her eggs. As long as we leave her and her babies alone, she wouldn't bother us. We have only one door, I would rather put it at the entrance of this building. It's not much but better than nothing. " Since they don't have carpenter's tools, Gintarou considers if he can use rope to attach the door at the entrance. Also he wants to add some noise making traps outside the building that will warn them if someone is trying to give them a night attack. @Druquilla

" I'll take the second watch. And Kraven isn't in a good shape. He should take the last one."

( What kind of check will be needed for the door and traps? )

I forgot to respond to the bottle question, I will say that if no one has any, someone just pay a silver to say that you had bought some at some point.

I would say that you are able to set up a door to block the lizard.

About 30 minutes after collecting the items and started to ready a guard shifts as Gintarou is setting up the door he hears a noise from the outside, and walking to him is The Voice of The Mother.  "The Mother is not happy, she wants you all dead."  behind him walks in 3 Infected Oahtu.

What do you all do?

:edit because posts at the same time.

(I'll take the coin hit since I forgot I wanted to buy a flask anyway.)

Mist smiles and winks at Gintarou. "That's good thinkin'! You know... It's convenient that you're a giant, hulkin' glob o' testosterone, but really we brought you along for your superior mental capacity. Let's see what you can rig up!"

"Right, then. Kraven should rest until the end. That means just 3 long watches. Sounds perfect to me."

As the Voice talks, Mist wordlessly grabs two of the newly-acquired potions out of his bag and hands them to Kraven (sorry, wanted to highlight it but not let it get confused with Mist's dialog) without taking his eyes off the newcomers.

"Don't know why she'd want your companions dead, but she certainly sent you lot to the right place as we're happy to oblige." The halfling stops and raises an eyebrow. "Or did you mean us? Because I don't really see her desires being fulfilled by the likes of you pissants."

Mist casts mold earth and excavates a 5ft cube of earth from one side of the door (outside), and re-piles it to block the entrance. Nerd stuff in spoiler.

@DM, is it safe to assume this Voice has a different body rather than still wearing the Gaius suit?