We also seem relatively safe in here and could use this place to rest and recuperate  (long rest) if we rest long enough

Quote from Flyingmatthew >>

Time in the Doomvault: 0 Days 15 Hours 30 Minute (Earliest next long rest 1 Days 3 Hours. So in about 11 hours. 

That was posted just before we entered this chamber, so I think that should be evaluated if we're gonna talk long rest because there's still 11 hours we'd have to wait before we even start our 8-hour long rest.

"It's as safe a place as any to camp, I suppose," Eiren says. "Though it's only been a few hours since we slept last. I'm pretty exhausted, but not tired. I feel like we should be pacing ourselves more. But all that to say...I'm alright camping here, as long as we can work out how to get out in the meantime."

Potion of Climbing: The smooth wall is hard to climb without aid. I'm going to say a Climbing Speed is a small aid. So if you have a Climbing Speed I'm going to set a DC if 20 Athletics check. Assuming you have a Climbing Speed of 30 feet, you will need to make two checks to make it to the vaulted ceiling. On a successful DC 20 Athletics check, make a 2nd Athletics check (11 or lower you fall 30 feet taking 3d6 falling damage, 12-19 makes as many checks until you succeed or fall) 20+ you make it to the vaulted ceiling and can find a reasonable place to climb around and/or make perception checks, ect.

Dispel Magic: I'm going to say that you need to dispel a Eighth level spell, targeted on one of the skulls. (The base spell teleportation circle + a combination of a third level curse spell.)

Eiren did you see my reply to your Intelligence check?

You will have to wait about 11 hours before taking a Long Rest, but yes this is a good place to take one, especially if you figure out how to get out first, which may take a few hours. 

“I’m going to call Qu’oth back to me,” says Eiren. “I’ve been using our mental connection to look at our previous surroundings, but it occurs to me that he might be of more use here, since none of us can scour the ceiling like we have done with the floor.”

Eiren pulls Qu’oth through the familiar’s pocket dimension and into the room with him, where the bird pops into existence. He then directs his familiar to examine the ceiling and upper area of the room thoroughly. 

Have Qu'oth make 3 perception checks. If he is still the owl he has Advantage on the checks. 

Qu'oth owl-eyes Wisdom (Perception): 21, 9, 11

"Think it's worth trying to dispel magic on one of the heads? Maybe we can end whatever spell is causing us to end up back here."

(8th level spell would make it DC18 with a +5 modifier on my roll, so definitely doable, if not the greatest odds one could ask for)

(Could Eiren help by expending his last 2nd-level spell slot?)

A Dispel Magic could indeed work. If we’re looking to grapple up to the ceiling, we could always tie the Rope to my Spear, and throw it at the wall.  I can fix it at any moment as well. Baik thinks for a moment. There’s got to be a spell he can use to get them out of here.

(Could I roll to see if Baik’s heard of anything like this weird room before? If so, 16, +5 if that would be an Arcana check.)

"I'll give it a shot," Corvin says.  "I can try a couple times if necessary, or even more if we end up down here long enough to get a good rest in."

 He walks over to the head he fell through into the room originally and tries casting Dispel Magic (18)

Qu'oth flies around the room looking for anything odd that you in the floor can't see. He spots a secret door  20 feet above the ground in the Northwest corner of the room.

Because it is only 20 feet up, if you use the Potion of Climbing it will be only 1 check to reach the door. And because it is in a conner I will reduce the DC to 16.

Eiren: No I will not let you help with the Dispel Magic with your 2nd level spell slot. I might have considered it if you had access to Dispel Magic.

Baik: Your idea with the spear is a good one, but I didn't think a spear would be able to embed itself firmly enough to hold the weight of a person. Maybe an arrow would work better?

Corvin tries to Dispel Magic on one of the skulls (2 or 5?), but fails. 

// Hey guess what, it helps to look at your character sheet. Apparently I've had a grappling hook all this time, lol //

While looking in his bag, Eiren exclaims with surprise. "Ah! I forgot I had this." He produces a grappling hook, which he will tie onto one of the lengths of rope he has remaining. He will then have Qu'oth fly it through an anchor point on the ceiling, close to the secret door in the corner. 

"This should make the climb a little easier."

Xavier opens his eyes and peers around as if woken from a hibernation sleep for the past 3 or so months

Anybody home?

Quote from Teechu >>

Xavier opens his eyes and peers around as if woken from a hibernation sleep for the past 3 or so months

 Lol

Eiren ties his newly discovered grappling hook to a rope and throws it up  After a couple of tries the grappling hook catches on one of the ceiling beams near the secret door. If someone uses both the potion of climbing and the rope they can make it to the secret door without making a roll. 

Any volunteers?

Velmine rubs her eyes, shaking off the sleep that suddenly overtook her all of a sudden. After a little stretch, she's all back and raring to go again, ready for more adventure. "If all you need is someone to drink a potion and climb a wall. I'd be fine putting myself first on the line. If the plan's to keep that potion, you might wanna ask someone with a little more upper body strength than I."

Eiren will volunteer to help someone else climb up first, allowing them to stand on his shoulders for a boost.

Corvin looks up at the secret passage high on the wall.  "Who's the most nimble?" he asks.