Navrine gets an idea and pours some water out of her wineskin onto the dusk tile so see if it has any effect?  “Just following the poem on the wall, maybe the water will disable the trap?” If that works she will use the torch on the last one.

From the area Chromir had rendered safe, Navrine emptied her wineskin upon the next mosiac tile and waited.  Nothing happened.  

Then she entered the area to lower her torch upon the last tile and after stepping on the mosaic, the trap activated!  Blades came scything out of the wall straight toward the monk!

@Johnny2136, please roll a Dexterity save [DC15], 8 slashing damage on a failure, 4 slashing damage on a success.

(Navrine rolls 22) She recoils taking slashing damage from the trap, "Ouch, that hurt!" She examins the wound "Well I guess the poem has nothing to do with getting by these traps! Shall we just get more ruble and try and break the trap with rocks?"

Don’t forget that Navrine has, and is proficient with, thieves’ tools. 

Navrine curses herself for not remembering the training she had growing up on the streets and pulls out a set of thieves' tools. “Guys, do you mind if I try something?” She sets about carefully trying to disarm the trap.

(Sleight of Hand: check 18)

((Couldn't you have started with that? ;P))

Navrine crouched low, producing her thieves' tools. Carefully, she prodded at the mosaic tile, discovering the boundary of the pressure plate that had been setting off the trap.

A final, delicate click echoed through the corridor, and the deadly blades locked back into their slots, inert once more.

The second trapped area has been disarmed. There are two doors at the end of this hallway, one to the north and one to the west. For the characters with ongoing effects, about five minutes have elapsed since the combat with the rats.

"G-good job. That was trickier that I thought," Cassian says to Chromir and Navrine, relieved that the cruel blades will be a danger no more. Though their methods were vastly different, the two are both ingenious in their own ways.

Cautiously proceeding towards the doors, he studies them both carefully, looking for any possible traps or mechanisms.

Investigation: nat 20+4

"Doc, could you tell which w-way that big creature was?"

West

((Ok, he will still study both doors))

((Navrine will help Cassian in investigation by helping to spot locks or traps trying to give him advantage))

If Doc shares that the creature is west, Chromir will express his desire to go show that creature who is boss (and hopefully, the answer is Chromir, and not the large creature....) 

Otherwise he doesn't have a preferred door 

With Navrine's assistance, Cassian examined the pair of doors at the end of the passageway. 

Each of the doors were simple, wooden affairs.  Unlocked, and not sturdy.  The bottoms had been chewed away over the years, allowing all manner of rats and other vermin to easily bypass the doors.

Through the dwarf's stonecunning, Doc knew that the door to the west held dozens and dozens of minuscule creatures scurrying about as well as something quite large.  Through the door to the north, he sensed no movement.

@Secretfool, Doc will be the tiebreaker.  Which way shall the party go?

Doc looks at the others and thinks its best to take care, if it is hostile, of what is behind the door at the west, such that they are not surprised when doing anything else.

The door creaked open, revealing a room that had once been a laboratory but now lay in charred ruin. To the left, a nearly disintegrated desk sagged under the weight of decay, its surface littered with shattered alchemical glassware and scorched residue. In the center, a set of tall bookcases, arranged back-to-back, stood like skeletal sentinels, their wood blackened and splintered by heat.

The destruction worsened toward the back of the room, where thick, opaque webbing cloaked everything in shadowy tendrils. It hung from ceiling to floor, sticky strands glistening faintly and obscuring whatever might lurk within. As the heroes stepped inside, something crunched underfoot. A glance downward revealed the charred hindquarters of a giant rat, its body burned and brittle.

 Attracted by the noise, in one of the corners, a swarm of spiders appeared!  Dozens and dozens, if not hundreds of tiny spiders began to spew forth out of the webbing!

Deep within the webbing — a faint rustling sound could be heard — a warning that something far more dangerous was watching from the darkness, hidden among the tangled silk!

Our next combat encounter, gang!  Please roll init and let me know your actions. For ease of tracking movement, everyone can begin counting off their movement as if they are at the hallway-side square of the doorway.  The opponents will act on 16 & 7.  The swarm is init 16, and the opponent with init 7 is hiding within the webs. Please include a disadvantaged Wisdom [Perception] roll vs DC19 with your first post. (Regardless of the outcome of Doc's perception roll, he can still sense/target this large beast with his Stonecunning)

The area is unlit, save for Navrine's torch.  The purple area is an area of webbing.  This webbed area counts as Difficult Terrain and is Lightly Obscured.

Doc Init: 16
Doc Perception: 23/24

Doc steps into the doorway, throws a spear at the bigger opponent, and steps back into the hallway to make room for his companions.

Spear throw: 15 to hit, 9 dmg.

Cassian init: 17

Perception with disadvantage: 7

Cassian will head 10 feet left and then 15 feet down and ready an action to attack if an enemy comes near him.

Readied action: Longsword to hit 16, damage 5

Navrine Init: 23
Navrine Perception: 16/14 (So with disadvantage 14)

Navrine darts through  the doorway,  and will head 10 feet left and then 10 feet down and ready an attack, if an enemy comes within 5 feet.

Readied action: Unarmed attack, to hit 20,  damage 8 points.

Chromir will not pay any attention to the charred corpse which may well signal another trap, fire based this time. Which could also explain why the webs are not this far over. 

Init: 19
Perception with dis: 6

With his 35ft of movement, Chromir will charge at the spider swarm, still raging, and take a swing with his greataxe hoping to hit as many spiders as he can.

21 to hit for 5 slashing damage.

(I assume that despite it being a swarm, they are one creature for the purposes of cleave, so I don't get a second attack)