Ilezenya flies back down to the ground, happy that the team was able to open the door. And then deflates as they see the portcullis blocking their path. He doubts there will be a lever or handle on this side, but he'll look for one regardless. He'll also try to see through the gate to find the lever or opening mechanism on the other side. (Perception:13 in game log)

Illezenya is unable to identify either a locking or lifting device for the portcullis.

"Hmn. Credit where credit is due. It was wise of them to bar the way double so in case of such intrusion. Though this significantly limits our options." D.O.R.K took a moment to give the bars more than a cursory once over, and even gently wrapped them with her knuckles to test both their quality and possible arcane defenses. If nothing then untoward comes of her tests, she turns to the others and says, "Once I've fully gathered my strength on the morrow, I can request of the goddess for a means to navigate around these bars. But as things stand at the moment, our only other option would be to camp out here or at the base of the mountain, wait until they open up, and then try to sneak or force are way in. Though given the extreme danger and our own limited capabilities, it is not advised." She confesses.

D.O.R.K then looks a little hesitantly to Torunn. "Unless you have another idea, b-.... Acolyte Torunn? As you are far more knowledgeable of craft and engineering tricks than I or anyone else here, or so I suspect."

Torunn looks at the bars and the device with an expert eye, trying to discern their inner workings and asking himself if he could lift it just enough to allow the others to pass he also test if he can pull it up. ( percetion 17 or 13 investigation. He will test if he can lift it athletics(?) 22 ) 

Are these rolls sonewhere

Ilezenya also adds, "I, too, must wait to the morrow to regain all of my abilities and powers from my goddess. If there is not mundane way to open or bypass this gate, then I suppose we are commandeering one of the yakfolk structures!"

Quote from GrantFromCanberra >>

Are these rolls sonewhere

 ( In the game log sorry!   

Toruun manages to lift the portcullis above his head high enough for the party to scramble through  “quickly” he urges them “I can’t hold this forever.” When the last party member is through he lets the portcullis go with a grunt. As the party is now over 60 feet into the mountain there is insufficient light for those without dark vision to see much. Those with dark vision (Torrun, Beedo, Vark, Illezenya and Mullo) can see they’re on the edge of a vast chamber with a diameter in excess of 150 feet. In the middle of the chamber is a large shaft, an iron rig is is bolted to the rim of the shaft.

Party order and what’s next pls? 

"I see that we're on the edge of a vast chamber that's at least 150 feet across. In the middle of the chamber is a large shaft, with an iron ring bolted into it. Let those of who can see go ahead to check for any enemies, then the rest of you can light a torch and join us in half a minute." Ilezenya tells the group in a low voice, not wanting his voice to carry to far. If the group agrees, he will go with Torrun, Beedo, Vark, and Mullo deeper into the chamber, looking for any threats skulking about or traps waiting to snare them. (The Dusk Warden has 300' darkvision, so he can see the entire chamber...)

Still feeling rather... 'upset', to say the least, for not testing obvious solution sooner, D.O.R.K upon finding her way into the chamber (along with her goblins) simply nodded an agreement, before posting up by the portcullis on the off-chance a hasty retreat proved necessary. And though able to see into the gloom to some extent, Vark seemed about ready to follow D.O.R.K's example unless specifically called into action. But Beedo more than happily joins in the expedition with his new weapon in hand and every intent to do a bit of pilfering of things found in the chamber.

-Beedo's Stealth: 18.(27)

-Beedo's Search For Goodies Traps in chamber: 2.(18)

(@Grant: Regarding the weapons chest(link here), was the etc. part a catch all for any non-magical weapon of the player choosing from like the PHB? )

(Including ammunition as well.)

Yes within reason i.e. normal weapons - no gunpowder or anything really strange

Mullo moves forward, fanning out in attempt to spot any dangers before they can catch the group off guard.

Perception: 19 + 1; if at disadvantage: 5 + whatever the second roll was

Devins moves into the chamber as quick as he can, Aslan flying right with him.  Once inside Aslan lands on his shoulder and looks about.  Devin's eyes glaze over as he begins to look through Aslan's eyes (60 ft darkvision, Within 60 feet of the tressym, magical invisibility fails to conceal anything from the tressym’s sight.)

Devin stays with the group without darkvision though and lets Illezenya and the others scout ahead.

Toruun walks in with the others and tries to discern more about the iron ring and possible utility. 

( Investigation on game log: 14 )  

After ducking under the portcullis, Ebonitus stays close by Devin, keeping one hand on his shoulder, to make sure he does not get separated and waits for his eyes to adjust somewhat to the gloom.

(OOC  - working off the phone so apologies for any typos)

As those with dark vision - including Devin via Aslan - explore the huge chamber further they discover there is an 80’ diameter shaft in the middle of the chamber which appears bottomless. An iron rig is bolted to the side of the shaft reaching out to the middle of it. A chain runs over a pulley in the rig and disappears down into the darkness. The other end of the chain disappears out through an aperture in the southeast wall through which the can be heard the sound of rushing water.

Adjacent to the aperture there is a metal plate bolted to the wall. Approximately 10 feet off the ground is a 3 foot iron lever protruding from the iron plate.

As the party peers down into the chamber there is a clanking of chains and the chain starts to move towards the aperture in the wall.

"Get ready - we're about to have company..." Ilezenya says softly to those around him. He then moves to the lever by the aperture and motions for the others to join him. "Let's try to move that lever and stop whatever is coming up on that chain!"

Mullo hurries over to help Ilezenya.

Both Illezenya and Mullo look up at lever approximately 4-5 feet above their heads and say simultaneously “that’s right this place was designed by giants!”