Once all of the others have exited, Dagna will follow.

Stool takes Edwin up on his offer, climbing up to his shoulder. You all move out quickly, and head back towards where Jorlan told you the armory was. The shrieks, wails, and humming still echo all around you. Then, you get a great glimpse of what exactly is making the sounds as they fly near one of the Drow towers. 

Three large, insect-like monsters are chasing two giant vulture-like ones. The humming comes from the beating of the insect monster's wings, and the inhuman shrieks come from the vultures. They twist and snap at the insects in the air, while the insects try to stab the birds with the needle-like proboscis:

The monsters take no notice of you, busy fighting amongst themselves. You still hear the drow shouting at each other, but it seems to be from another part of Velkynvelve.

Nacht looks at the large insect monsters with an expression of fear, then runs even faster toward the armory.

Edwin:

Using this distraction as effectively as possible, Edwin keeps moving towards the armory as well.  He takes care to move smoothly so Stool has an easy time holding on. Hampered by his manacles, he hopes to find a means of releasing them in the armory.

As you're running, you come face to face with Jorlan. He stops short, looking at you with wide eyes, fear evident in them. Whatever this is...it wasn't me. If you're smart you'll get out of here quick. He takes off towards one of the other towers.

The armory is unmanned, but far from empty. There are drow weapons lining the walls, from hand crossbows to short and long swords, drow poison, and drow leather armor. There is another table to the side with Dagna's spellbook, component pouches, and what looks to be the equipment you had on you when you were captured.

(How long do you spend gathering items? You can each grab two items per round, keeping in mind you'll need something to carry this stuff in as well. There are a few backpacks slung to the side as well. You don't see any rations in here, unfortunately. The more that you grab, the longer it takes, and the more likely you are to be spotted. The less you take, the less equipped you may be to face the trials of the Underdark.)

Edwin:

Round 1:  Edwin starts by grabbing his backpack and the serviceable hatchet he has used on many a tree trunk in its time (starting equipment that could reasonably fit in a backpack, perhaps?)

Round 2:  He then grabs a likely looking backpack (one that looks kinda full) from the wall without taking the time to check its contents, then looks around for a set of keys or tools that might be used later to free people from their manacles.

Perception Check if needed:  23

(Further round(s) actions depending on how long the rest of the party wants to stay.)

(No keys, but there is a blacksmith's hammer you could probably break the chains with once you're out of danger, it will take you to round 3 to grab it since you spent some time looking)

Round 1: Dagna rushes over to the table to reclaim her spellbook, as well as a component pouch to ensure she won't be rendered so useless ever again.

Round 2: She too grabs a random, seemingly full backpack off of one of the hooks without checking inside, as well as a dagger.

Nacht yanks a shortsword and an ornately carved stone (casting focus) from the wall, then searches for something to use on its chains.

*supplies are for the weak*

Karys is briefly distracted by the sight of the strange insects and vulture creatures, but she quickly gathers herself and joins the others in the armory. They don't have much time to grab their belongings unfortunately.

Round 1 - Karys grabs her longsword and light hammer.

Round 2 - Karys too grabs a random, full backpack.

Round 3 - Karys grabs a light crossbow and pack of twenty bolts.

Edwin:

Grabbing the blacksmith hammer and a spare Longsword, Edwin rushes out of the room ready to leave their drow captors behind!

(3 rounds total)

Dagna moves to follow Edwin hurriedly.

Nacht glows with energy as it runs after the others.

*readying a spell for 2nd round*

(Karys, those are hand crossbows, not light crossbows)

Elspeth rushes in as well, and exclaims as she runs to the table with your equipment. My hammer! And my shield! Thanks the gods...let's get out of here! She hefts a huge, ornate warhammer and a shield with what looks to be some sort of crest emblazoned on it. 

Jimjar and the other gnomes grab shortswords and hand crossbows, Buppido grabs a dagger and a shortsword, and Derendil grabs nothing since his claws are as sharp as any sword in the armory. The drow grabs a shortsword, hand crossbow, and a couple vials of poison before dashing back out as well.

The drow leads the way now, jumping over the side and into the webs, then struggling loose and diving off into the darkness below. Elspeth takes a deep breath, looks back at the crew, shrugs, and dives off as well. The other prisoners quickly follow her.

The four of you are left. You see drow scampering down the hallway away from you, but their backs are to you.

(Athletics or Acrobatics check to see how gracefully you make the dive)

Nacht dives over the side and brute-forces its way out of the webs. 

Athletics: 22

*There's the roll I was looking for*

Dagna holds onto her spellbook for dear life and jumps over the edge.

Acrobatics: 18

Edwin Athletics:  23

Trusting his life to the drow’s insteuctions, Edwin makes the leap!

Karys leaps over the edge, not quite as gracefully as she hoped.

Athletics - 11

Nacht dives and barely feels the webs, tearing straight through. Dagna hits on her back, and rolls gracefully over the side, never losing hold of her spellbook. Thrown off a little trying to protect the tiny mushroom, Edwin nevertheless tears through the webs as soon as he hits and continues his fall. Karys, likewise, tears through the webs after she hits.

You all fall for what seems like forever in the darkness, but is really only seconds. You see the pool rushing up towards you, and then you are suddenly plunged into the icy water. You see the others surfacing, trying to get their bearings. The drow is scrambling up the rocks, out of the pool already. High above, shrieks and wails continue to echo around the large chamber.