Saoirse successfully cuts away the largest poisonwood vine without touching the hairs or sap - especially thanks to a swift and precise cut from Lam's great axe. Hemlock speaks to the plant, and it does seem like some of the hanging vines shift slightly out of the way, making it easier to see the whole door of the hut. The plant doesn't speak, not in any way that any of you understand, but Hemlock is somehow reminded by a slight rustle of leaves of the hissing sound of a feral cat.

It looks like the door to the hut could be opened with a simple turn of the handle on the door.

Saoirse didn't understand what Hemlock had said to the plant, but imagining what it might have meant, she felt a little bad that they had been so eager to cut it. She muttered an awkward "Sorry" which the plant, of course, wouldn't understand, much less reply to. Her skin still itched a lot, and as she rubbed it, she realized that the sap could actually be of use. Surely, the same could be said for the poisonous frogbear mucus. That was, after all, what she had been discussing with Tesfaye: to look for ingredients she could work with to boost her weapons.

The genasi turned to Hemlock. "Could you tell the plant that I'm sorry, and that since I have already cut it, I will try to put its sap to good use?". She then took a couple of crystal vials from her backpack and took a sample of the sap as carefully as possible. (Reagent gathering: 17 / Nature: 12) "Just a minute,"  she added before running to the nearest frogbear body to do the same with some of its mucus. (Reagent gathering: 23 / Nature: 2). 

With that taken care of, Saoirse approaches the door, making sure her friends are ready before actually opening it slightly. She'll take a quick peek inside to check what is inside before doing anything else. (Perception: 18)

Hemlock passes on Saiorse's message, then waits patiently for her to gather the samples, not wanting to get too close to the vines himself in his current state.

He looks up to Shah, wondering if the tabaxi can see anything from his new perch.

Sha waves and points finally calling down, “Something huge a tentacled horror in the water!!”

Lam follows Saoirse to the door and stands behind her with his greataxe ready to attack anything that comes from the hut. He turns in alarm when Sha mentions a tentacled horror to see if he can see what his feline friend has spotted.

Saoirse manages to take a sample of the poisonwood sap, but it is still an unknown species to her, and she learns the hard way that the vines and leaves leave an itchy rash as well. It is annoying amd unsightly, but not actively damaging.(The rashes will go away when she next heals for any number.)

Similarly, she manages to gather samples of bear frog slime, but she underestimates the viscosity of the mucous, and a vial leaks slightly as she  tries to put it into her bag. It drips on her lunch - ruining it. She manages to successfully gather one sample.

When you open the door, you find... A smallish room, pleasantly furnished with cushioned, carved wooden furniture. There are paintings of elven canoes and kayaks, and of noble children playing in clean water. There are some scuff marks, and old rotten crumbs around in the room, as well as a small pile of papers on a coffee table in the middle. 

One corner of the room has a collection of fishing tools and water sport gear.

There is a large conspicuous hatch in the floor, carved of beautiful wood and not concealed, on one side of the room.

Lam sees a long, greenish tentacle splash up out of the lake, and take purchase on the shore. What it is attached to is about to pull itself out of the water.

Saoirse's heart begins to pound with anxiousness when Lam and Sha warn them about the tentacled creature emerging from the lake. Her breath catches for an instant, and then she dashes toward the hatch they just discovered, praying it leads to a hiding place from the horror outside. Ignoring most of the room, she notices the papers on the coffee table and glances at them quickly (Investigation: 12) to see if they reveal anything interesting, and grabs them to examine later.

Despite the urgency, the genasi inspects the hatch closely. Does it seem safe to open? Is the smell of rot they detected outside coming from here, perhaps? (Investigation: 19)

Hemlock does not need another invitation to enter the hut, as soon as the tentacle appears he gets inside.

He looks across to Saoirse as she checks out the hatch.

"That must go under the water. Or perhaps an observation point to see under the lake", he thinks out loud. "Perhaps there is something in here to help us breathe under water", he adds, as he starts to look through the gear in the corner.

Investigation: 14+1=15

Lam stays out right by the door of the hut and watches Sha to see if he’ll also go inside. He stands with his greataxe ready.

The gear Hemlock finds is very fine quality recreational lake stuff, but unfortunately nothing that would allow breathing underwater to any real degree. There are canoe paddles, and something similar with a paddle on both ends of the shaft, though Hemlock is not familiar with kayaks. There are also some spongey, round balls that would clearly float, some strange glasses that sit tightly to the face, and a few fishing rods (the barbed hooks make you gasp at the cruelty of them), and a small net. 

The notes Saoirse looks at are written in Dwarvish, recognizable but incomprehensible to her.

The rot smell is definitely coming from the hatch, it is unlocked, and it would be easy to throw open and descend.

Lam and Sha see a huge creature begin to rise out of the lake. its face is generally froglike, though the eyes are on stalks. Instead of forelegs, it has four long, prehensile tentacles that it uses to help pull itself out of the water. Its mouth has lines of sharp teeth, and you have every reason to believe it has a springloaded tongue like the frogbears did. It balances its bulk on two froglike legs. It sniffs the air, and searches. One of its tentacles wraps around the bottom of the trunk of the tree Sha is perched in. The creature is much too large to fit through the door into the hut.

Sha-gravis says a quick prayer to Shar/Selune, then using charger runs down the trunk and uses his cat’s claws to deliver a savage slash at the tentacle.

Move plus feline agility.  
Action attack with charger for extra damage.  
attack 21 damage 9

”Run for your lives!”

Saoirse doesn't need to see what is going outside. As soon as she registers Lam's expression as he watches the creature in all its splendor and hears Sha, she yells "Down the hatch. Come on!!". She opens the hatch and starts descending as quickly as possible so as not to block the others.

Hemlock grabs hold of the strange glasses, curiosity getting the better of him, and them moves to the hatch with Saoirse. He does want to see what is down there though, before blindly jumping in, mainly due to the smell of rot coming from below.

"Careful, I dislike the smell, and the likely cause of it".

Hemlock hears the blood hunter's muttered voice coming out of the hatch she is already descending. "I don't like it either. But for the moment, I prefer it to the thing out there."

In any case, the genasi heeds the druid's advice and before her feet hit the floor, she'll try to assess this new room. (Is it in darkness? Will those without darkvision be able to see?) (Perception: 5)

Lam will not go inside the hut until Sha is inside. If Sha runs inside, Lam will follow as quickly as possible and shut the door behind him.

Sha having seen multiple tentacles keeps a sharp watch as he prepares to cautiously disengage towards the cabin at his earliest opportunity.

Under the hatch is only intense darkness, darker than her eyes can pierce, clearly magical in nature. There is the smell, now you can localize it to coming from somewhere west of the brief stairs down from the hatch. There is also a repeating, whispering sound, difficult to make out. You can hear that the room underneath the hut must be significantly larger than the room you're descending from. 

Outside, the Froghemoth's tentacle recoils in surprise from the vicious attack. Sha, Lam, roll initiative. Saoirse and Hemlock must roll as well if they decide to engage the monster.

Lam sees that Sha is not safe yet, and prepares to engage the monster.

Sha’s preparing to defend himself and disengage if possible.

Saoirse climbed the stairs again enough to poke her head through the hatch. Still talking in a hushed tone, she transmits what little she's been able to gather to Hemlock, then adds "Are Lam and Sha still out there? What is happening?"