((Piercing damage to Zokk is halved to 7,  but Zokk is grappled!))

The squad attacks to remove the last small bug threat.

25  Squad attack

32 Squad damage

If the last small bug falls, the squad will move.  Trying to move further into the cave but a bit away from the rest of the allies so that if the great big enemy has a huge fire or other area attack, they are all not grouped together.

Randy, Dornikal and Zok, blessed (just a reminder to remember to use it)

Coljin's squad dispatches the last small bug and moves in to take position at the edge of Randy's lantern's bright light (which I'm realizing has just been attached to Randy regardless of having a hand free for it).

((Zokk's squad to attack, then Ulmwin and his squad. If we don't hear from M0rt, I'll post something.))

"Well that is one dang big ugly critter now isn't it?!" Ulmwin shouts, a bit perplexed... But soon orders his squad to move up just the slightest bit to the edge of that bright light, throwing javelins. He himself will keep up his thrusty fire bolts for the time being, trying to move up and behind that pillar his squad is next to.

Attack rolls: 16 8

8 1

Bughunters:9 22

At the end of Ulmwin's turn, the creature slashes at Zokk with the appendages next to its mandibles.

Attack: 22 Damage: 14

Dornikal bites his cheek and dashes over to the beast, blood shining on his teeth.

(Or normal moves if the cheek biting is an action)

The big beastie, a bit puzzled at not finding soft flesh, tosses Zokk and begins to move further into the room.

((Zokk, you'd have an opportunity attack if you wish it. I have you at 6 HP currently, fyi.))

((Since Zokk is pilotless at the moment, I'm going to say they forgo the opp att, as it would focus the ire back on them...))

The creature moves into the room, on the far side of Coljin's squad, and hissing, unleashes not fire, but a soft green mist that washes over the four dragonborn and Dornikal. 
Randy, on the far edge of the mist feels the coolness on his cheeks and momentarily grows groggy, but manages to shake it off.

((Con Saves from Dornikal and Coljin's squad. Not poison, so no dwarven bonuses to it.))

((Was a little hasty, let's see if he can attack or what...))

Con sav: 9

Bless bonus:4

Dornikal slumps into slumber...

Squad save!  16

The squad wavers on their feet, but stay up!

((The Party is up!))

Zokk's squad will attack (and hit if Zokk hits)!

Zokk darts in and beats on it with their staff, trying to stun it. (Spending ki on each of 2 hits to force DC 14 CON Save. CON Save if needed: 24 and 14)

Attack: 17 Damage: 7
Attack: 15 Damage: 12 if Stunned: 11
Attack: 19 Damage: 10 if Stunned: 25

All three of Zokk's blows impact the hard carapace to no effect.

Zokk has Bless!

Rolling to see if he hits on second or third attacks: 

14 + 1
15 + 2

Zokk's staff clatters off, but as they jam a wooden knee into the creature's side, it shudders and goes still for a moment, before shaking it off.

((Legendary Resistances Used: 2))

It whirls on Zokk, snapping with its mandibles.

Attack: 8 Damage: 15

((Legendary Action Used: 1))

Dornikal snores fitfully.

((Want to roll for the dragonborn?))

Randy shakes his head to clear it, and shouts a warning. "It's spray can put you to sleep!"  He holds position to fire, then backs past Ulmwin to put more distance between him and the bug (up near the wall).

Bow attack 1: Attack: 9 Damage: 11

Bow attack 2:Attack: 18 Damage: 11

Bless bonus: 2

If within 30 ft Planar warrior: 3