Humblodt will cast Charm Person from a place of concealment (are we dousing the candles in this room first?) when the nearest thug is visible (DC13 Wis). 

Stealth 28
Initiative 19

If charm succeeds, I’m hoping he’ll try to stop the fighting (“you’re all my friends...”)

Thug's perception 13

Thug's initative 19

Jasper Wis saving throw 12

Horace Wis saving throw 8

Roars defeats the third Redbrand in the room effortlessly, while the other two fall under Humblodt's charms. 

Deleted

Humblodt charmingly convinces his new friends that we're going to prank the unconscious thug by leaving him in a cell guarded by skeletons. Meanwhile, the party puts on the red cloaks Ro liberated from the storeroom. When Horace and Jasper are ready to go the party picks up the unconscious man and follow behind the thugs as they lead the way through the crypt.

Horace and Jasper go north into the dusty passage and show you how to step around the trapped floor. They open the copper door and you follow them through into the next room.
Three large stone sarcophagi stand within this dusty crypt, and propped up against each sarcophagus is a human skeleton clad in bits of rusty mail. False columns along the walls are carved in the image of spreading oak trees. There is a door in the northern wall and another in the north-east corner that they head towards.

Humblodt puts on a quiet giggle (which isn't easy for the taciturn dwarf) and talks in hushed tones to Horace and Jasper, telling them that we will put the unconscious one in the cell while they should go and get some of the others they are friends with to see the jolly jape. He tells them that Glass Staff would never think its funny and, anyway, he is the boss...you don't discus pranks with the boss. While they whisper, Twiglet carefully listens at the North Eastern door, ready to sound the alarm if he hears anything that implies any guards inside might come out.

Perpection 14

Assuming Twiglet doesn't need to raise the alarm and assuming Horace and Jasper agree, they head off in a comedy "shh....quiet" kind of way and the party gather round the North East door, ready to storm the room. Ro and Tally at the door and Humblodt and Twiglet just behind. The supernatural quiet of Humblodt's charm still making their movements as quiet as velvet.

Twiglet hears some quiet sobbing behind the door and two harsh voices laughing and jeering.

Horace and Jasper leave through the Northern door, as they leave you hear them bickering between themselves about whether "those big furry blokes that arrived yesterday might like the prank"

With some quiet instructions, Tally and Ro stand either side of the door, Humblodt and Twiglet stand back, Twiglet ducks behind a sarcophagus with a quick, worried look at the old grave. Humblodt casts his cantrip Druid-draft to douse the candles in their room. Twiglet uses his fingers to count down from 4...and gets to 3 when Ro shoulders open the door anyway and rushes inside. Tally follows her in with his mace, Humblodt readies his sling and Twiglet sights into the lit doorway, looking for a silhouette to to aim at.

Initiative:

Ro: 22 (from Bot)

Twiglet 9

Humblodt 9

Tallanvor 0

Attacks:

Ro: Second hand hits for 2 (from Bot)

Twiglet Attack: 18 Damage: 12

Humblodt Attack: 24 Damage: 6

Tallanvor Attack: 14 Damage: 7

The two Redbrands look up in surprise as a feral goblin breaks through the door leaping at the closest of them. An arrow takes the same thug in his side while a pellet from Humblodt's sling hits him in the head.

"Anthony" shouts his mate before Tallanvor strikes him with his mace.

Redbrand Initiative 14

Humblodt will follow up by trying to hit the Mark with his Shillelagh. 
Attack: 12 Damage: 4

Ro spins towards Marcus and stabs at him with the shortsword.

Reckless Attack: CRIT Damage 10

Reckless Offhand Attack: 20 Damage 3

Marcus doubles over as the sword sinks into his abdomen so deep that the tip pokes out through his back. Seizing the rare opportunity, Ro rears back and headbutts him as hard as she can. His nose makes a terrible crunching sound as it breaks.

Marcus slips in a pool of his own blood and collapses, unconscious.

Ro wipes Marcus's blood from her face and glances around the room. Seeing the caged slaves she turns around and kicks Marcus savagely in the teeth.

This long room is partitioned into three areas, with iron bars walling off the north and south. Filthy straw lines the floors of those cells, the hinged doors of which are secured by chains and padlocks. A pair of disheveled human women are held in the cell to the south, while a human boy is confined to the north. All are dressed in plain gray tunics and have iron collars fitted around their necks.

A heap of discarded clothing is piled carelessly against the far wall.

Tallanvor attempts to stabilize the thugs. He finds it difficult with a sword going clean through the torso.

Medicine: 23

Tallanvor succeeds in stabilising the thugs. Both remain unconscious.

Ro ties up the thugs, pulling the knots as tight as she possibly can. They will probably not be comfortable when they come to.

Twiglet pulls out his lockpicks and attempts to unlock both cages. Ro brings out her tools and offers to be a spare pair of hands to make it easier for Twiglet.

North cage (Dex + proficiency in thieves' tools): 25

South cage (Dex + proficiency in thieves' tools): 15

Both cages swing open. The slaves inside look scared of you, believing this to be some sort of trick and shuffle as far as they can away from you.

"We do be here t' set ye free, this no be a trick, but we do need yer help. Y' see we must wear these cloaks t' avoid suspicions from the guards. There do no be much time to explain. We want to put these redbrands in a cell, but ye must all go t' the other one. Follow me, we will no lock the cell once ye are in in, and y' can escape the way we did come once we leave."

The boy in the northern cell hesitantly leaves his cell, then runs towards the southern one hugging the two women. The older woman looks at Tallanvor and says "Thank you"