The bandits exchange looks and eventually seem to come to some decision, and whatever it is, it doesn't seem to include kicking Bryn and Arren out of the tunnel. The Elf then sits just where the senior bandit was sitting until recently. The Human remains standing, and he seems wary of the soldiers. The Elf looks slightly more careless and eventually answers Bryn's questions. "Do you not? Maybe the sickness isn't; people are often sick at this time of the year. But finding a place like this by chance? Even if most rumours are exaggerated, there is sure to be some truth behind them. Gold, gems. Maybe even magical artefacts? One doesn't just 'stumble' upon places like this."

When asked about Nohem, the bandit seems to harden. "Why do you care? Indeed, we attacked first, but I still didn't get the impression you two care much for our safety that night." He pauses for a moment, looking at each of your faces. While he doesn't look exactly resentful of the soldiers, he sure isn't friendly, either. "I don't blame you for your actions then, but I don't see why it should matter to you now. If we all just died as they did, wouldn't it be easier for you?"

But before Arren or Bryn can respond, a cry echoes from deeper into the tunnel. "Help!" It sounds panicked, which surprises both bandits. They share a confused look for a moment, but the Elf soon dashes into the tunnel, leaving the Human to block the tunnel, who stands there intending to fulfil his part.

Please act on initiative from this point, unless you choose to wait and observe the situation from where you stand. You may post in any order, though I'll assume Bryn reacts faster if actions interfere with each other, as he was more prepared for this situation.

Arren lifts his gaze to the sitting bandit, ready to answer the remark that their deaths would make things easier. But the words never leave his mouth as the cry from the tunnel snaps everyone's attention away. He turns toward the passage at once, taking a step forward, only for the Human to move and block his path.

Arren stops short. "You hear that?" he says in a low voice. "That's your best-equipped man calling for help."

He flicks a glance past the man, toward the darkness beyond, and then back to him, insisting, "Are you so confident that your companion will be enough to handle whatever's happening in there?" 

A beat. If the Human still doesn't let them in, Arren adds, coldly, "Nohem is already injured. How many more of your companions do you want to end up the same way? Make your choice. And be quick about it."

Action: Persuasion 11+5=16
(If the man is convinced, then Arren moves 30 feet into the tunnel)

'Tace' listens to the elf speaking about how they had died, and tried to place him at the attack when he killed one of their number. But then the panicked shout comes from the senior bandit and the elf disappears down the tunnel leaving just the wary human.

He purposefully doesn't react too quickly, even though he had been expecting something to happen. The guardian wasn't exactly fast, well not compared to me. I wonder if it took the bandit by surprise. 

The Sergeant speaks first, obviously keen to go and see what is going on, and is typically authoritative. A man of action, the Sergeant can't help but respond to a cry for help.

He waits to see what the human bandit will do, and also to see if the other two bandits make a hasty retreat, whilst being prepared to follow the Sergeant if needed.

Action: Ready Dash - following the Sergeant if he is let through.

The man looks hesitant, and it even seems like he's going to stand in Arren's way despite everything, when suddenly a second call comes from inside the tunnel: "Nafnlaus! Get a light and come here, NOW!" It is the voice of the second bandit, the one who just dashed away a few moments ago (OOC: I'm stretching this a little to speed things along, so this round took a little more than six seconds), and he sounds frantic. Hearing the call, the Human moves out of the way and passes around Bryn and Arren, on his way to the nearest lantern, giving the two an opportunity to run ahead.

After passing the short passage and running in the tunnel for a bit (altogether would take you 2-4 rounds, I've skipped ahead because I imagine you'd only dash, but if there's anything else you wish to do, you'll have the time), Bryn reaches the same fork in the tunnel he saw last night. Arren, running a bit slower (since Bryn can dash twice each round), a little behind him, and finally, Nafnlaus, carrying the lantern behind them (about 30 feet behind where he appears on the map). The only light source around is the oil lantern carried by Nafnlaus, spreading bright light up to 30 feet away and dim light an additional 30 feet away.

"Those damned plants! I've finally cut myself free! Hold on, I'm coming!" Akvedinn's voice echoes between the tunnel's walls.

Party's turn. Currently, neither can see what's happening, but can hear it coming from the left side. If they come within line of sight of the room, they'll see that, in addition to everything previously described to Bryn, thick vines now cover the ground, at least an area of it, and they seem to move around, trying to hinder Akvedinn as he slashes them with his sword, trying to walk farther north (the green rectangle is difficult terrain).

'Tace' dashes forward but slows down with the aim of moving more stealthily at the intersection when he hears the elf bandit shout about the plants. Having seen the guardian, and the pulsing of magic through the roots the previous time he came into the tunnels, he is not surprised when he sees the thick writhing vines to the left.

He turns to the Sergeant and points to his eyes with two fingers, and then to the north with one finger. He then moves stealthily into the Northern tunnel, knowing that it leads to the same room.

Action: Hide - Stealth: 4+6=10 (oops)
Bonus Action: Dash
Movement: 30ft up the north tunnel so he can look into the other room

Seeing the Corporal move north, Arren advances to the fork and from there, he dashes toward the left passage—just far enough to get a clear look at Akvedinn struggling against the unnatural overgrowth that seems out of place in this man-made cavern.

He doesn't push farther in. The vines would slow him too much, and he can't yet see the full room. "What's happening?" he calls out sharply, ignoring whatever remark the bandit may have about his presence there. "Did something attack you?"

With no immediate answer and no clear way forward through the vines, Arren prepares to shift his approach and follow north instead, in search of a less obstructed path, hopefully.

(Movement + Action Dash until he is close enough to spot Akvedinn.)

Bryn starts sneaking into the northern tunnel, perhaps hoping to flank the creature with which the bandits are (presumably) struggling. But as Arren runs westwards behind him, paying no mind to silence whatsoever, his chain mail clanking with each step, Bryn realises any hope at stealth is doomed from the start. Unfortunately, it is too late.

What previously looked like another mass of roots suddenly shifts, and Bryn recognises, a second too late, a second vine-guardian. It looks about like the first one, but Bryn can find enough differences to believe it is not the same creature - if those are creatures at all.

Before Bryn can react in any way, the guardian burrows its "hand" into the tunnel wall, and almost immediately, a mass of grasping plants sprouts from the ground around Arren and Bryn. The vines move, trying to coil around their limbs and restrict their movement.

Meanwhile, Nafnlaus continues running towards the tunnel, just appearing beyond the turn. In the other room, Akvedinn makes his way through the entangling plants and disappears out of view. Too focused on the task at hand, he doesn't answer Arren.

The maps tool was giving me problems so I ended up using a different token for the second creature, but to Bryn, they look similar enough to believe they are the same type of creature (in other words, same stat block).

The second vine creature used his reaction to cast Entangle. Please make a Strength save DC12 or become restrained. If restrained, you or another creature can spend an action to try freeing you from the vines with a DC12 Athletics check. In either case, the green area is difficult terrain. Although I didn't mind telling you, as players, what spell was cast, both characters are unfamiliar with the spell.

Lastly, since this was the creature's readied reaction, it happened during the round, and as such, Arren still has his action, and Bryn still has his bonus action for this round, as both were Dash actions that might be affected by the new circumstances. If you wish to change your course of action following this, please post it along with your save. Do not post the actions of the next round yet, as the vine creature still hasn't acted on its turn (I've already moved the bandits since they won't be affected, though. I'm sorry if that's confusing in any way). To lift any doubts, Arren has used up all his movement so far, and Bryn used up his action and 15 feet of movement.

'Tace' is not expecting the restraining vines, and is wholly unprepared to resist them.

Strength Save: 4+1=5

(OOC: That will teach me to use Bryn's action for something his bonus action can do haha)

Arren quickly realizes he's made a mistake. He should have followed the Corporal's lead. He should have kept quiet. Instead, the clatter of his armor has announced far and wide, and now the tunnel itself seems to answer. What he had taken for another mass of roots shifts, and in that instant his blood runs cold. "What in Aleshi's hell is that!?" he snaps.

Despite the surprise, the Half-Elf is able to avoid the worst of the growth. In the back of his mind, a harsh voice shouts that he's been too careless. That he should have seen this coming. What kind of example is he setting, blundering forward while his subordinate moved with caution?

For a flicker of a moment, he considers rushing back to the Corporal's side to help him out of the vines, but he's too far. So, Arren decides to reach for one of the two javelins he's carrying.

"Duck!" he barks, and then he hurls the weapon toward the vine creature. If he can strike at it,  maybe it will loosen its hold on the vines.

Strengh ST: 11+6 = 17
Action: Throw Javelin at the Vine creature. To Hit: 12+6 = 18 / Damage: (5, 2)+4 = 9. The creature becomes Slowed. 
Superiority Die (Goading Attack): The Creature must make a WIS ST DC 14 or have Disadvantage on attack rolls against targets other than Arren until the end of his turn. Die roll = 8. So the total damage is 9+8 = 17.

Arren's masterfully thrown javelin pierces the vines and gets stuck between them. To any person, even most animals, this would be a lethal hit. But this creature, although hindered, remain standing. Arren thinks he still damaged the creature, it's just sturdier than an average person.

The creature steps forward, standing just at the edge of the grappling vines area. From there, it extends a lengthy arm-like vine, trying to wrap it around Bryn's neck to strangle him! But although the grappling vines severly limit Bryn's movement, the creature is also somewhat unable to move freely with Arren's javelin impaling it, and so Bryn manages to free one hand momentarily to hack at the extended vine and protect his neck.

 The creature failed the save to Arren's manoeuvre (rolled a total of 9) and then missed its attack against Bryn, rolling a total of 11 to hit. It is now one square under where it was in the last map (10 feet from Bryn). Other than that, no changes.

Party's turn again.

Arren's mouth presses into a thin line when he sees the creature is still standing, but there's no time to dwell on it. He advances at once, moving to Tace's side and trying to tear him free from the vines. Then he steps forward, putting himself between the creature and Tace.

Action: Free Tace from the vines. Athletics check: 8+6 = 14
Movement: Advance forward to stand between the creature and Tace.

If Arren can reach the creature: Action Surge (Attack with the Longsword) To hit: 6+6 = 12 (not sure if that hits?). Damage: (6, 1)+4 = 10 . If it hits, the creature becomes Sapped. (Can I circle past the creature, without moving away from it, to allow @volcano to reach it?)

Reaction: Impose the shield if Tace is attacked.

'Tace' does as bidden, and ducks out of the way of the javelin as best he can whilst being restrained by the vines.

When the Sergeant surges past him, tearing him free as he moves, he breathes a sigh of relief, "Thanks, Sir. I have no idea what it is, some kind of creature made of vines. Perhaps Gaitha is not as pleased people have found this place as the bandits think. It must be guarding something though. Something important or valuable".

Even as he speaks he draws one of his daggers, takes careful aim so as not to hit the Sergeant, and throws it at the vine creature.

Bonus Action: Steady Aim (give advantage but reduces speed to 0)
Action: Attack vine creature with a thrown dagger (with sneak attack due to advantage)
Dagger (with Advantage) - To Hit: (2, 6) + 6 = 12 (Miss!)