Mullo surreptitiously use Thaumaturgy to try to open the doors. They fail to move which leads you to believe that they may be jammed.

"Have you tried pushing the doors?" Mullo asks.

Before Mullo asks "Have you tried pushing the doors?" he remembers that earlier on (post #3849) Devin had described that several of barbarians were grunting as they shoulder charged the doors which are not moving!

"Hmmm,"  thinks Ebonitus, "I wonder if either of those frozen levers have anything to do with the door opening mechanism?"

Ilezenya continues to watch quietly from the shadows, ready to help if things turned ugly...

"This is clearly getting you nowhere," Mullo finally says, her shell of humble reverence cracking. She turns and waves a hand, her strings of beads and bones tinkling. "What are these ledges?"

Chiief Wormblood looks up at the ledges and shrugs his shoulders "don't know - now can you help us get through these doors or are you as useless as the other witch over there?" pointing to the Shaman

(Looked back to previous posts and the map you posted earlier. I was a bit confused and thought that we were in a room, but I think now that we are still in the passageway that ends in the door the other barbarians are trying to force open. Additionally, 
"...2) there are a series of ledges 20 feet above the corridor extending from a point 100 feet into the complex to a point 200 feet into the complex
3) carved into the back of the ledges are a series of niches which all contain iron sconces
4) off each ledge there are series of entrances going back into the mountain")

Ilezenya decides to scout out the ledges above them. He focuses on Selune's blessing, and rises into the air. (You can draw on the mystical power of night to rise into the air. As a bonus action when you are in dim light or darkness, you can magically give yourself a flying speed equal to your walking speed for 1 minute. You can use this bonus action a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.) He will move up to the ledge to the west, flying along the ledge and looking into each corridor leading further in to the mountain. He will then investigate the ledge to the east. He is looking for another way into the complex, or some additional clues.

Ilezenya decides to scout out the ledges above them. He focuses on Selune's blessing, and like a ghost rises into the air and starts to move along the corridor to the left (northern side). He glides about a foot above the ground and thus avoids making no noise for the moment. After a bit over a third of a minute (4 rounds) he finds his way blocked by a heavy iron portcullis 20 feet wide by 30 feet tall, with a 30-foot-high wall above it, blocks this 60-foot-high passage. The bars of the portcullis are ice cold to the touch and spaced far enough apart that a Small creature can squeeze between them. He recalls from the description Devin gave them the southern side is probably exactly the same. 

(OOC: with his remaining 6 rounds of flight what Illezenya want to do - noting it will take four rounds to return to the party.)

While this is going on Mullo has been engaging in conversation, well actually a bit of a shouting match with the barbarian chief while his warriors continue to shoulder charge the door.

(Can he fly around the portcullis? If it only blocks the ledge, can't he go around it? =) 

Blocks the passageway - sorry if that’s not clear. You can see them in post #3864 as dotted lines

(Ahh - I see now! Too bad we don't have any gnomes in our party! After spending a few seconds investigating and looking through the bars to see what lies beyond with his 300' darkvision, the dusk warden will return to the group and quietly tell them what he discovered. All except Mullo, who stands in the light and focusing the attention of the other barbarians!) 

D.O.R.K, as stalwart as she was, almost tenses when Ilnezya's voice suddenly comes out softly from the darkness. She then nods after receiving the intel, knowing the half-drow at least would see the motion. Then in keeping her words brief and quiet as to avoid attracting too much attention their way, the following is spoken: "Noted. At least none will escape or can slip our notice there. Stay vigilant." Afterwards, assuming Mullo moved closer/had moved closer to the doors, so too would she, gently tugging others along if need be so that they stayed relatively in formation while maintaining the usual distance just outside of torch light.

After spending a few seconds investigating and looking through the bars to see what lies beyond with his 300' darkvision, the dusk warden will return to the group and quietly tell them what he discovered. 

Illeznya informs the party that forty feet beyond the portcullises it opens out into a huge chamber. The chamber is so big that even with his enhanced dark vision he cannot see the far side. (OOC: This is the same chamber that Devin is scrying but as his spell only moves at 30' per round he has not seen as much). Given that Ilezenya is 40 feet back from where the chamber starts he can really only see in a very narrow beam. 

While we are in the huddle, Ebonitus repeats his thought (in a whisper) "perhaps the frozen levers back in those side tunnels are to open the doors. Also, I wonder if anyone considered that the doors may open toward us? The other question I have is 'Why is Wormblood tryin to get in?'"

As Devin overhears them talk of opening the doors he moves the Arcane Eye towards the door on the inside to see how it may function.

As Devin overhears them talk of opening the doors he moves the Arcane Eye towards the door on the inside to see how it may function.

As Devin examines the door he can't see any door opening mechanism - what he can see however is the patina of ice covering the inside of the doors.

Mullo locks eyes with Wormblod and moves so that she is directly centered with the doors. She grabs the piece of pegasus hoof hung around her neck and chants a quick incantation while waving her free hand. At the conclusion of her casting, a strong wind blows from her directly at the center line of the two doors, irrespective of anyone in the way. (She's also hoping that the wind will blow out all of the torches, leaving everyone blind but her.)

Action: Gust of wind

Picture this: There are six barbarians - three either side of the centre - pushing on the doors. Wormblood, his dragon and the Shaman (well outside of the reach of Wormblood's arm are on Mullo's right (southern side of the group).

Mullo summons the power of her god and a huge gust of wind springs out of nowhere. As the barbarians are clustered around the door - i.e. a bit closer than 5' apart I'll allow it to directly impact four of them - Saving throws are as follows (18, 7, 23, 11) and one of them is slammed against the door. As the wind bounces off the door it swirls and blows out the torch that the Shaman was holding. "Where'd that wind come from?" Wormblood yells out (OOC: he is at least twenty feet above Mullo and 55' feet away) but the Shaman doesn't answer.

The doors remain closed!

When Ilezenya hears about the ice covering the back of the doors, he whispers - "We need heat to melt the ice - then perhaps the doors will open..."