Yes-  Lorlin will take a watch, if we are staying.  

Akkron only needs four hours to Long Rest, so he'll be able to take over the watch for the remainder of the night as soon as he's rested up...

"Just so everyone is aware... the Forcecage will only last for an hour... so we should really figure out what to do with the man inside of it. My hope is that we can convince him this whole thing was a misunderstanding and part ways amicably, but since I can't speak Celestial there is little I can do to facilitate coming to such an understanding."

Slip can take first watch

Dabbert will take a watch.  I'll make a longer post tomorrow. :)

Akkron will take his long rest and mix up his spell list a bit in preparation to do some pretty intense spellcraft. He'll ritual-cast Identify to figure out exactly what this blade the warlock had is and if it does anything. In any case, the monk was apparently willing to risk his life to get this weapon back from a powerful Warlock. The lich would rather not make an enemy out of the Monk if he can be persuaded that the whole fight was an unfortunate misunderstanding... but Akkron also doesn't want to risk handing a dangerous magical artifact over to a potential enemy if the Monk can't be won over.

(If I'm understanding things correctly, the Monk has said that the Warlock stole the blade from the temple and that's how the confrontation happened, right?)

Dabbert takes a watch, and he walks his post while his friends rest.  He frequently checks the Monk, making sure that his bindings are secure, but not hurting him, and also that he's as comfortable as he can possibly be.  He does what he can to communicate an air of gentleness and respect, but doesn't try any other form of communication, since he hadn't shared a common language with the monk earlier.  

He checks the windows frequently too, looking to see what is going on outside, to see if they're being aggressed by assault teams of the stone-warriors, or if any of the flying Beholder's have found a way through their 'defenses'.  

Akkron, your identification spell lets you know that the sword  belonged to the warlock, and was in fact his hexblade. (I’ll DM you details).

Shadows lengthen until the tower falls into cold darkness, even as the sky outside remains in multi-color limbo. Fog becomes frost that creeps up the tower, providing some cover from the monsters below along with an icy sleep. 

For what happens in the middle of the night, I’m going to need a perception check from y’all.

 Dabbert, since it occurs when you are on watch, you’ll have advantage. I will also need to know how exactly you’ve bound the monk…

(PM to the DM; I'll make my post with rolls and details after I get an answer because it will effect what I do.)

Perception: 12

...that's kind of sad, adding 5 from Knowledge from a Past Life to that.

While not openly hostile to the Monk, Dabbert sure doesn't trust him.  The last thing he wants is for the fleet footed bastard to get loose in the middle of the night where only one of them are up to deal with him.  That could be bad.  Real bad.  He secures the monks hands behind his back with a pair of manacles and then binds the manacles and wrists all to an immovable rod that he locks into place in such a way that the Monk is leaning back.  It has to be uncomfortable, and Dab hates that, but he doesn't want the Monk being able to squirm free.  

He's not as worried about the guy's feet, but for all he knows the Monk has razer sharp toenails from hell, so he binds his feet as well and stretches them out away from his body and locks them into place with his other immovable rod.  

"Please....uh.  Just don't."  Dab pleads with him.  "Please?  Please.  Take uh...a nap or something."  

He keeps his head on a swivel while walking his post...

The ornery monk eventually succumbs to his exhaustion. Between his wooden armor and the immovable rods he at least has good lumbar support. Akkron takes a watch, noting the wide berth given by occasional monsters who crawl by below. At the changing of the guard, Dabbert's militant watch detects nothing odd outside or in as the shadows turn black. Keeping time is weird here but you manage to maintain some temporal stability by counting steps and shadows. Because of this, you know for sure its been 2.5 hrs when the monk wakes up and begins screaming.

It's still a garbled celestial but their meaning is clear as the monk coughs out high pitched-guttural howls of pure fear. Thrashing, he manages to get a hand loose in a shower of splinters,  which shakily points into a shadowy corner of the tower. 

By now all of you are awake, though don't see anything that the monk is pointing at... 

Except for Slip who has dark vision. 

Slip stands and says to the team "We are not alone". 

To the stranger he says "Hello traveler. How can we help you?"

Dabbert, alerted by Slip, brandishes his halberd and calls Alala into action, letting the shield float before him.  He steps between the tied monk and the newcomer that Slip faces, making clear to the monk that no harm shall come to him from this being he fears.

"Everyone uh...easy now."  Dabbert says.  "We don't want any trouble."  

Akkron sighs.

"I guess a night of peace and quiet was too much to hope for... Let's see what we're dealing with."

Akkron uses Prestidigitation to light up one of the lanterns so that we can actually see the intruder.

You all see the swordsman emerge from the shadows, dark leather bag in hand. “Relax folks, I’m just here for the body,” they say, kneeling by the fallen warlock. “It’s unfortunate, but undertaker is one of the few careers that still remain from back when.”

Unfolding their valise, they somberly lower the warlock inside and then colapse it close. You don’t hear any crunching so it’s probably bigger on the inside. 

Growing more rattled, the monk continues with his wailing, bellowing his fear of “the reaper.” The new figure ignores them.

“Lynn was never one to lay low, and that’s usually what keeps you alive around here.” Finishing their work, they make their way toward the door as the monk utters the first quiet thing you have heard from him.

”Holy and undefeated.”

With that he slaps the button on the immovable rod with his free hand, grasps his temples, and with a demonic grin, lifts his head from his body with a final scream.

“Apologies,” the newcomer sighs. “They tend to do that.”

"I was about to use that corpse to make a... oh, never mind," Akkron sighs.

The lich is taken completely off-guard when the monk somehow rips his own head off. He stares in shock at the decapitated body. 

"That... was unexpected," the lich says dryly. "I suppose now we know what happened to the guy in the bathroom..."

Akkron pulls out his pipe and lights it up. He's been in worse situations than this before... but never in a place that just felt so incredibly wrong in a way that he couldn't quite put words to.

"I uh...how...what..."  

Dabbert looks at the monks headless corpse and blinks, unsure of what he just saw, or why. 

"Who uh...who are you?"  Dabbert says, remaining wary of the newcomer.  "What happened here and why?"  

"Those are very good questions," Akkron says. "And if this is your job... who is paying you to do it? Are there other survivors in this gods-forsaken place?"

“I’m the undertaker here,” they reply. “At least for those like this warlock here. For the beheaded over there I’m page doctor.” They take up their bag and move over to the monk, doing a post-death analysis of sample and note taking. Vials of fluid and pages of notes are filled with findings and dumped into a different carrying case (this one appears to be a portable hole). The immovable rod is clicked free and the monk tumbles forward and is scooped into the portable hole after the undertaker retrieves something from its pocket. 

They toss a severed, ornate pocket filled with diamonds on the floor. “Looks like Lynn tried to get his portal components from the wrong people. Stealing from an order of monks is never recommended but these were never a real order so I can’t blame him. I’m not sure if it would have worked either , but I have to admire his faith. All I can do now is  extend an invitation to you all to attend his funeral. If your ok with a midnight stroll?”