Swin reappears and pokes the glowing F4 with her rapier, while casting green flame blade

Attack: 21 (with adv) Damage: 3 plus a whopping 1 fire damage

If she can two-weapon fight, she also tries (tries) poking with a dagger

Attack: 7 Damage: doesn't matter

"Rhane, we're coming!" she says, trying not to act like she can see anyone behind the guard down the hallway.

I think you would need to have attacked with your main action in order to bonus action attack with the dagger? So no, as I understand it. A hit with the rapier, though. :)

Brigands 4 and 5 attack Swin, who has just popped back into existence: crossbow bolt fly, for 17 against AC, 7 piercing damage, and 7 against AC, nada.

Fighter 6 turns with an expression of fury on his face. "I've been looking forward to this, worm", he says, and attacks Rhane with his mace: 20 against AC (not nat 20) for 5 points of bludgeoning damage, then 17 against AC for 6 bludgeoning.

He remains locked in combat with Rhane.

Alton and Kef are up.

Alton gets to where he can see into the room better and fires off a crossbow bolt.

Action: Fires a crossbow bolt at Fighter 4; Attack: 22, Damage: 8 Piercing

Alton, you fire, and see Kef fire at the exact same time, at the same target. Both bolts hit, and together are enough to finish off Fighter 4.

Round Four:
Balassar
Brigand 3
Darren and Rhane
Fighter 5
Swin 
Brigands 4 and 5, and Fighter 6
Alton and Kef

Balassar is up.

Balassar moves five feet diagonally to flank fighter 5 bringing his sword at the fighter as he moves and engaging brigand 4 with a follow through strike. He then looks at the unengage brigand and begins to just stare at him like a snake trying to charm prey as he begins to speak in a low rhythmic draconic hum try to charm him as a rune glows on his blade.

OOC:
Movement: 5 ft diagonal to flank fight 5

Attack on Fighter 5: 12 (5+7) to hit for 5 damage

Attack on Brigand 4: 27 (nat 20 +7) to hit for 11 damage + 1 damage from Giant's strength

Also, why not going to try and invoke the stone rune on Brigand 5 this turn: DC 14 wisdom save, if he fails, the creature is charmed by you for 1 minute. While charmed in this way, the creature has a speed of 0 and is incapacitated, descending into a dreamy stupor. The creature repeats the saving throw at the end of each of its turns, ending the effect on a success. Once you invoke this rune, you can’t do so again until you finish a short or long rest.

Slice!
Fighter 5 takes a serious wound, but is still up.

Slice!
Brigand 4 is cut almost in two, and drops dead to the ground.

Brigand 5 looks on in shock, and then his face clouds over and he sort of sags where he stands, staring into nothing (Nat One on his save).

Brigand 3 shoots a crossbow at Balassar (16 against AC, misses). He stays where he is.

Darren and Rhane are up.

Darren attempts to finish off fighter five while he’s distracted by the towering Dragonborn (hit:13(w/adv) dmg: 12 slashing) should his attack finish off his foe. He will move to get a better angle on the hallway. 

Rhane:

Taking two hits from the condescending bandit guard, Rhane struggles but is able to maintain his concentration on the Hunter's Mark (Constitution Saves 16 and 14).

The weaponless warrior replies, "Your time as a blight upon this land is nearly finished--we will eradicate you like and unruly thornbush," as he strikes again in quick succession, this time with a punch to the right temple and a fake to the left arm, disguising a powerful roundhouse kick to the ribs...

Punch:  13 to hit and 12 damage

Kick:  21 to hit and 7 damage 

Darren, you do claim the scalp of the Fighter, and so you move to where you can see Rhane, in combat with another powerful-looking enemy.

Rhane, Fighter 6 (known to you as Racker) is completely flummoxed by your speed and agility; it seems he can't wrap his brain around the fact that his prisoner is beating him, to within an inch of his life. 

Swin is up. Fighter 6 is very badly wounded, Brigand 3 still has Faerie Fire, and Brigand 5 is staring off into nothing, unable to defend himself.

Swin is up.

Swin targets Brigand 3 with scorching ray, rolling at advantage due to Faerie Fire.

1st ray: 
Attack: 11 Damage: 6
2nd ray: 
Attack: 17 Damage: 8
3rd ray:
Attack: 13 Damage: 8

She then darts 40 feet toward Rhane (think he can just get to the NW of Brigand 3). "We're here!"

One miss, two hits, enough to bring Brigand 3 down.

Brigand 5 does nothing, and appears not to be about to do anything.

Fighter 6 is too busy furiously smashing his mace at Rhane that he doesn't appear to notice that he's effectively alone. First attack is a nat 20, 13 bludgeoning damage; second attack is a 13 against AC and misses.

Alton and Kef are up.

Alton moves into the room behind Balassar, standing on the table he fires a crossbow bolt past Balassar and Darren to try and hit the fighter down the hallway.

Movement: Moves 25ft into the room to get right behind Balassar and stand on the table.
Acton: Fire a crossbow bolt at Fighter 6; Attack: 14, Damage: 11 Piercing.

Rhane, Racker is so angry there is spittle coming from his mouth as he snarls and starts to speak. And then there is a crossbow bolt in his mouth. He topples, his last insult unspoken.

Kef steps in, and not really sure of what has happened to the last Brigand, he takes aim and shoots with his crossbow: 21 against AC for 4 points of damage. Does his state of confusion end when taking damage?

Round Five:
Balassar. Darren, Rhane and Swin
Brigand 5
Alton and Kef

Balassar is up.

Balassar just moves and swings at the brigand this time pulling back on his strikes to knock out the brigand remembering it might be good to question at least one of them.

OOC:

Movement 5 ft in front of Brogand 5

Attack 1 for 20 to hit and 9 damage non-lethal

Attack 2 for 26 to hit and 5 damage non-lethal

Giant’s Strength: 5 extra damage

So flavor text of the rune itself doesn’t says and I couldn’t find that it automatically ends on any of the effects. So gonna leave it up to your ruling, since spells that do this do typically have it ending after an attack.

Rhane:

”Swin, Darren, you came to save me!” exclaims Rhane warmly as he dashes up to the remaining brigand.  Holding on to his Hunter’s Mark spell (concentration save 11), he transfers it to the last enemy standing as he arrives.

(Bonus action to transfer Hunter’s Mark, Move and Dash to get adjacent to the brigand).

Balassar, you knock the brigand out. They are unconscious.

Combat is over.

“O’ course we did. We was… well at least I was getting worried about ya. What with it being so long since we heard anything from ya.”

Darren stands warily on guard alert should anymore brigands come out of the woodworks. 

Rhane:

”Thanks all the same.  I have been a prisoner of these bandits too long.  Let’s see if we can find my equipment once we have dealt with the bodies and you have introduced me to your new friends,” responds Rhane.

He ruefully looks at his wounds and adds, “It seems my combat skills are a bit rusty after my imprisonment.”

“I brought summat might help.” Darren cleans and sheathes his blade and rummages in his bag for a potion of healing. Handing it out to Rhane to take should he wish to.