The BFOAGWGH

On a string around her neck is a key shaped like an anvil. You also find a potion of healing in a pouch on her belt. On the table there is a sack containing the treasure that she has collected. The sack contains 190 ep, 130 gp, 15 pp, nine small gemstones (10 gp each), and a dwarven ale mug made of hammered electrum (100 gp).

The notes on the table discuss the history of the Forge of Spell and Phandelver. There are letters written in another hand which talk about how to overcome the magical defenses that are rumoured to protect it. They are signed Glass-staff.

Tallanvor takes the key and tries it on the door leading to where Humbolt said they would find the dwarf.

If he's unconscious, Tallanvor will use a spell to heal him and hopefully wake the dwarf. He splits the HP between him and the elf to stabilize and ideally wake her as well.

Channel Divinity: Preserve Life

As an action, you can use Channel Divinity and present your holy symbol to restore up to 10 HP divided among any creatures within 30 ft. up to half a creature's HP max. You can’t use this feature on an undead or a construct.

You open the door and heal Nundro who opens his eyes. You calm him down and explain what is happening. You heal the elf as well who groans but remains unconscious for now.

Twiglet suffers Ro’s embrace which seems to have too many elbows. This strange goblin is a confusing mix of frenetic rage and puppy-dog eagerness to please. One thing is for sure though, Twiglet is glad Ro is on his side.  Twiglet squeezes back and assures the little warrior that he is fine. 

"yer brother hired us t' come lookin for ya" Tallanvor says to the bewildered dwarf. "Let us leave this cave and get y' back to safety. Can y' walk?"

Ro picks up all the letters and notes and helps Humblodt stow them in his tinderbox to keep them dry.

On the way out Ro will take a quick pass through the room where they found Gundren's brother to make sure they didn't miss anything.

Investigation: 13

"Thank you very much. Is Gundren far? Does he know about Tharden?"

Roars sees nothing of interest in the room that Nundro was imprisoned in. The lock and door look reasonably strong so the room could be secured against from the undead roaming around. However from her experience, she guesses it wouldn't resist an angry bugbear for long

"We need to know if those Bugbear things are friends of the elf." whispers Twiglet to Tallanvor, as they prepare to leave. "Can you ask....Nundro?"

Twiglet also offers to go back via the route that will give him visibility of the door to the Bugbear room door. If he hides at the corner of the crossroads outside their door (the one he previously trapped), he can keep an eye on it at that point and see when the rest of the party emerge from the flooded tunnel into the room with the lake in it. If the Bugbears (or anyone) comes out of that room, he will retreat towards the temple with the aim of then doubling back under the flooded tunnel.

If the trap is already  sprung or dismantled (and we didn't hear it) then I retreat immediately, as it means the Bugbears are out already

Stealth, for watching the door 8

Stealth, for retreating (if necessary) 19

Nundro tells you that when he and Tharden were attacked the dark-elf had 3 bugbears and 2 hobgoblins with her. One of the bugbears killed Tharden.

The trap remains ready and you still hear the bugbears arguing inside. Twiglet sneaks around the corner seeing the rest of the party exit the secret tunnel. He kicks a pebble which bounces down the stairs. The bugbear voices suddenly stop and he hears loud foot steps approach the door. He jumps down the steps to join the rest of the party, hearing a crash as his trap falls on the unsuspecting bugbear that was first through the door.

Hearing the trap go off, Ro moves to the wall next to the foot of the stairs and holds her action. If she sees anything other than Twiglet coming around the corner she'll pounce on it.

Attack: 18 Damage: 7

If she sees Twiglet pop out of the tunnel or come down the stairs she'll stay right behind him as they flee the cave.

From his position at the corner, North of the Bugbear room, Twiglet shoots an arrow at the closest target, then with the bonus action, Twiglet will run loudly to the flooded tunnel scattering some ball bearings as he goes (you never know and I just checked to see he has some) and then swim through as quietly as he can.

Attack: 18 Damage: 7

The second bugbear steps through the door over it's fallen companion and is hit by an arrow in the shoulder. It gives a roar and starts chasing Twiglet. The other bugbear picks itself up and follows. 

Bugbear 1 Dex check 20

Bugbear 2 Dex check 12

Both bugbears make it through the ball bearings, but lose sight of Twiglet in the chasm cave.

Twiglet swims as silently as he can, then runs as if the very whips of his masters were on him. If the Bugbears seem close behind, he ducks East after the lake cave, to try to loose them in the tunnels, hoping he remembers the way

Stealth while swimming 12

Athletics while running 18

Memory of the cave system (my wisdom and intelligence bonuses are the same), if needed 9

Bugbear Perception 14

The bugbears cannot find Twiglet's trail. They call down to the goblins below asking if they have seen or heard anything strange. Finding nothing they go to report to their boss, but finding the temple as bloody mess with the table cleared they raise raise the alarm summoning the other goblins to find the trespassers and the elf.

Twiglet passes the Eastern tunnel entrance just as he hears bellowed shouts from the direction of the temple. That means they won't catch him...the thrill of the chase courses through his veins and he puts on a final spurt.

He ignores the rope hanging down the cliff face, the rock is roughly cut and there are more handholds than he would expect from a city house

10

His overconfidence is brought rapidly down when he realises the rocks are slick and wet...

As they retreat Ro scatters ball bearings at the base of the stairs in the pool room, at the entrance to the hallway leaving the pool room, and at both of the intersections with the maze that leads to the room where they found the ghoul.

Humblodt hurries Nundro along, carrying the limp and newly besacked form of the elf over his shoulder, heading for the cave mouth.

If we assume Twiglet gets to the top first...he will nock an arrow and take aim at the tunnel exit

Tallanvor shares in distributing the load of the elf. They will need some time to get that elf up the rope. He heaves himself up to the top of the rope as best he can with the weight of the chain mail fighting against him.

Athletics: 11

They'll have to hurry now that the alarm has sounded in order to hoist the elf up before the goblin reinforcements can gather.

"Move yer flamin' backsides less y' want t' be in a stew pot come mornin'"

While the rest of the party is working their way up the rope Ro throws one last handful of ball bearings down in the north entrance to the room. Then she moves closer to the rope, finds a hiding spot, and holds her attack until any enemies come within range (20ft).

Stealth: 18

Attack: 18 Damage: 4

She'll wait until all of the party members with ranged attacks have made it up the rope, at which point she'll climb up. If it's faster to climb the wall while the second-to-last person is on the rope she'll do that instead. (Plain roll: 9  Athletics is -1, Acrobatics is +3)