So 29 total

Xardorok Wis save DC 21 - STR DC 22 12 - CON save DC 16 18

Attack: 18 Damage: 8

Attack: 12 Damage: 5

Attack: 16 Damage: 13

Attack: 8 Damage: 11

Krom finishes off the last torturer as Rhogar grabs onto Xardorok to keep him from melee.  Gorrah stings him but he resists the poison.  Chill sees that the pope head is nearly spent and hopes one more shot will finish him off.  

Vellynne looks about and then rushes to a pile of gear in the corner and grabs a wand and points it at Xardorok and several bolts of energy slam into Xardorok killing him.

Kazri may redirect her attack on the pope head if she wishes as the torturer is dead and the only foe left is pope head.

(Kazri attacks the Pope Head)

Chill continues to do his best to avoid blasts of fire as he takes another shot hoping to finish off pope head

Attack: 17 Damage: 28

Same BA, action.  Same Uncanny Dodge reaction if needed.

Reroll 1d8 8

Kazri, seeing that things are under control heads down the hallway and strikes at pope head.  A moment later a bolt flies past her and slams into the duergar and he falls to the ground dead. 

A strange thing then happens.  

As the duergar falls dead his hat comes off of his head. Suddenly the body changes and instead of a dead duergar you see a whole different creature. Still dead.

Rhogar's eye went wide seeing Xardorok die in his hands. But without letting go, he shoots Vellynne a conflicted look between anger, disappointment, and grudging gratefulness, before letting his attention drift towards the others. Only then in seeing his fellows at least alive would he turn a harden gaze again on the corpse, slowly sets it down, and then began searching Xardarok's body as he says, "Unless one of you can speak to the dead or can recall his spirit for a moment, it seems we won't be getting our answers from the king any time soon. Not unless, Vellynne, the dwa--er, duergar's lips were loose during your time together. As we still have a bit of a dragon problem. Gorrah takes the opportunity of things seeming to deescalate for the moment to flutter over to Chill and begin circling about him and examining his injuries.

-Investigation: 14. (if perception would work as well, add another +2)

Krom shakes his head at Rhogar's question "I wasn't expecting to interrogate the dead today, I haven't prepared the proper hymn. We can speak with the warlord tomorrow, but I fear that he may not be very cooperative."
The dwarf turns towards Vellynne "What did the warlord and the torturers hoped to gain from torturning you? What they were after?"

Kazri wasn't expecting this turn of events. With her shield in front of her, she pokes the spiky creature with her sword to make sure it is indeed dead. "Does anyone has any idea of what this... Thing is?"

Nature: 13

Chill moves up the hallway and kicks the the hat to the side and drawing his rapier he pokes at the body.  He looks aside to Kazri. "I would think you, in tune with a god, would know what such a thing is.  For me, I would wager to guess some sort of devil or creature of the 9 hells.  But what is it doing here?  What is going on in this place?" He glances back over his shoulder to the room the others are in. "It sounds like they may be done in there as well.  This one is dead, maybe Rhogar or Krom have a better idea."

Chill heads back to the other room to see what is going on. "Uh, you need to see this.  That pope head duergar wasn't actually a duergar.  Its some sort of spiky devil creature. Something weird is going on here."

Krom, while waiting for Vellynne to compose herself and replies to his questions, turns towards Chill "That duergar was a spiky devil creature? I do not like this at all." says the dwarf shaking his head "Duergar are evil enough without being helped by devils. Or maybe the devils have infiltrated the duergar to push forward their wicked agenda. Anyway, we should assume that more devils are hiding within this fortress."

Krom asks to Kazri "Can your keen senses also detect fiends?"

(Sorry folks, I haven't used the feature I have forgotten about it.)

Kazri looks at Chill with a puzzled look, then she face palms herself. "Yes, of course." She closes her eyes for a second she ask Helm for aid in her vision, and inspects the room for evil. Specially the dead creature in front of her.

(Divine Sense - As an action, you can detect good and evil. Until the end of your next turn, you can sense anything affected by the hallow spell or know the location of any celestial, fiend, undead within 60 ft. that is not behind total cover. You can use this feature 4 times per long rest.)

Vellynne is able to catch her breath after yelling curses at the now dead Xardorok.  "The duergar caught me on behalf of the frost druids, who want to prevent me from finding Ythryn.  I am certain that Ythryn holds the key to ending the Everlasting Rime.  They brought me here and Xardorok tortured me because I would not give up the secrets of Ythryn." She is then able to compose herself more.  "It is strange. The duergar do not come out of the Underdark, they hate the light."  She hears what Chill reports.  "Perhaps there is some sort of fiend controlling Xardorok.   He said his patron told him to come up here and gain the treasures of the Ten Towns.  He went on and on about Deep Duerra, the duergar god of conquest, and that this was her will and I would not stand in their way."

She looked as Rhogar

"The dragon is some sort of construct, set on a path of destruction to prepare the way for more of his plans.  We must stop this thing."

Meanwhile Kazri uses her Divine Senses but sees not evidence of any other fiends about.

At a break in your conversation the sound of forge area beyond the door has now changed.  It sounds like fighting and the clash of arms instead of working.  

"This room is clear." Kazri states. When hearing of the sounds coming from the next room. She goes to the door, asks Oli to step aside so she can open one of the doors, and peak beyond.

Perception: 22

Rhogar seemed about ready to respond, but in hearing the clash let out a huff of annoyance and rose up from the body. "Seems where know where our guide had snuck off to." His eyes widen for a second before glancing around. "And Rekuberk too, by the looks of it... Maybe. Hmm... Regardless-...!" He turns on Vellynne.

"Seems there may yet be more fighting for us, as we still don't have our answer to the dragon problem. So, shall we join them? Or do we cut our losses here and hope to play catch up in leaving the Duergar to sort out the rest of their own mess? Or do we at least make sure that once their fight is done that the leave for their homes altogether? ... And hopefully, again, find... find someway, some tool, some command... SOMETHING left behind by the bastard Xardarok that might recall or halt the dragon from here."

(@Pal:Did Rhogar find anything on Xardarkok's body before the clash that looked interesting?)

"We have the Codicil Vellynne, as soon as we take care of the dragon construct we can start our march towards the Caves of Hunger and Ythryn." says Krom.
The dwarf turns his head towards the sounds of battle "It may be possible that other devils are still hiding among the duergar, if the faction supporting Xardarkok wins, a new warlord may rise and keep tormenting the Ten Towns. We should at least make sure that the faction opposing Xardarkok's views does not get overwhelmed."
Krom turns towards Rhogar "As the dragon is a construct, the forge may contain some useful information about it. If we do not find anything there, maybe the Throneroom holds the secrets we are after."

Chill returns back to the pope head body and searches the body and inspects the hat. Returning to the others "This one had its own chamber off of the room with the statue.  Perhaps there is more information there as well." he says reporting what he has found.

Rhogar checks the body of Xardorok and finds he wears chainmail and wears a spike gauntlet on his left hand.  He has little else of value on him.  Chill bends down to inspect the fiend and as he does so the devil vanishes in a cloud of black smoke and returns to the Nine Hells.  The only thing left behind is the hat that you surmise must be some sort of arcane item that allowed the devil to be in disguise.

Kazri moves to the door and peaking out she sees that they are no longer right next to the forge.  A  hallway is seen going around a corner to the right.  The sound of fighting can still be heard.

Vellynne nods.  "The dragon may be set on a course and cannot be recalled.  The codical may know more about how such a things works, ask it."  

(Are we joining the fray? I don't believe Kazri has the codical.)