Krom looks surprised by what just happened "That was unexpected". says apologetically the dwarf while taking a step back allowing Kazri to examine the man. "Who are you and why were you chained?" asks Krom.

Chill looks over his shoulder to see what is going on.  "Still quiet over here, nothing seems to be moving." he says from the entry point.

23

The man struggles against the bonds but is unable to free himself.  He looks over at Krom and starts to answer his questions in a language you recognize is likely Loross but cannot understand.  He sees in your faces that you don't understand him and he then speaks in common.

"My name is Xerophon. I am the servant of my master, Iriolarthas, who sent me to prison for disobedience.The wizard who runs this prison conducts horrible magical experiments on prisoners."  He looks fearful "I am afraid I might be next.”

Kazri doesn't think there is anyone else in the vicinity, but she asks Oli to check the area nonetheless. Oli starts to smell the floor and goes around the area looking for a scent that different.

Oli Perception: 14 (Sniffing around to see if there is anyone else in the area)

Krom scratches his chin, pondering the proper way to reply "Xerophon, this may sound a bit strange to you, but by Moradin's beard, what I'm about to say it is the truth. It is not going to be a pleasant truth, so steel yourself."
The dwarf clears his throat before continuing "Iriolarthas has kept you prisoner for a very long time, far beyond the natural lifespan of a human." says the dwarf in a compassionate tone "A lot of things have changed in the meantime. Ythryn crashed near the Reghed Glacier, and now an eternal winter, probably caused by the misuse of the mythallar of this city threaten to kill this whole region and beyond. We are here to stop that from happening, can you help us?"

Though it took a moment longer than it should've, Rhogar eventually let out a "Hm!" in surprise hearing common out of the man, before then almost immediately hurrying back over to the table. "Indeed! We've already heard something about a ritual being needed to access the inner most area of the city, but not the details of it. So any information you can furbish there would be a good start!" He said brightly.

Then as if only noticing the bindings after the fact, the dragonborn smiles apologetically. "I take it though first you would like to be free, yes? If so, we can perhaps manage as much! Though-" He glances sadly over to Krom, but continued to direct his next words to the prisoner, "Unless some other magic has been sustaining you up to now, removing these bonds might result in your immediate... death."

Oli sniffs around the room but there is no indication that there is anyone else in the room or has been in a very long time.

Xerophon looks confused.  "What do you mean a long time?" he asks as he tugs on the bonds again.  "Could you free me? I don't feel as if I am in danger of dying, though I am a bit hungry."

"Are those binding enchanted Rhogar?" asks the dwarf before turning towards the Tabaxi "Chill, your expertise in picking locks is going to be extremely useful in this instance, could you please take a look too?"

The dwarf searches his backpack for a couple of rations to share with Xerophon and proceeds to conjure some water from the Alchemical jug. "Here you go. It's not much, but it should sate your hunger."
"As for the matter of the time..." Krom turns to each of his friends for help "I fear that I may be a bit too blunt, maybe someone could take it from here..."

Rhogar's eyes narrow just a touch at Xerophon's response. And though not a paranoid soul by nature, he couldn't help playing back the man's words in his mind, searching for any sign of something being held back or duplicity within them

-Insight: 17.

But be all that as it may, an absentminded nod and the pulling out a familiar wand is his answer to Krom, prior to then speaking a command word and altering his own vision just a tad. If he sees no magic to speak of in the bindings or lingering on the table, then he indicates as much and delve a bit deeper to try and discern any particular schools of magic attached to it. But if not, then it is with more a smile that he assures the others.  "Look not to me, Master Krom, as you know all to well us Dragonborns -- well, most of us at least aren't of a mind to... how do you say? 'Sugercoat one's words'? Hmn! Such a curious idiom that is."

"Two thousand years... Well, give or take. You have been imprisoned here for about two thousand years." Kazri states with a matter of fact tone. "Yes, you have much to catch up, I am afraid, however, I am sure Professor Orb here will be delighted to fill you in." Kazri points to the Orb.

(I am going to take the current year is about 1495 DR + 340 when the empire fell?? Give or take.)

Chill looks at the straps as Rhogar looks around with his heightened sense for magic, but he detects nothing.  Chill can easily loosen the straps and Xerophon and the man pulls his arms out of the straps and sits up.  He rubs his wrists and then accepts the water offered by Krom. As he takes a drink Kazri drops the news of just how long he has been on the table.

His sallow complexion goes white and he chokes on the water for a moment. He struggles to speak "Two, two thousand years?" He asks in unbelief.  "I... I... I don't know what to say.  How can it be for so long, what kind of experiments did they do on me?" Tears well in his eyes and he drops his head.  "Give me a moment, this is a lot to take in."

At this moment Vellynne stirs and then speaks.  "A sequester spell would do that. When you cast the spell and touch the target, it becomes invisible and can't be targeted by divination spells or perceived through scrying sensors created by divination spells. Also, as a creature, it falls into a state of suspended animation. Time ceases to flow for it, and it doesn't grow older. That's how he could be here, still alive 2000 years later."

Xerophon speaks again "The wizard would cast a spell before leaving me. So does this mean Iriolarthas, everyone, is now dead?"

Rhogar judges that his reaction is genuine.

"From the information we have gathered, your former master Iriolarthas is dead, but death was not the end for him. His skull still haunts this city. According to the Professor Orb, he is now a demilich." replies Krom. 
"You are now free Xerophon, but as long as this eternal winter grips the whole region within its icy grasp, none of us are safe. We must stop the Frostmaiden at any cost.
Any information you can share about the mythallar, the ritual for entering the center pillar or the arcane artifacts of this city would be invaluable us."

Kazri calls Oli to her, she crouches and whispers something to him. The young owlbear waddles to Xerophon, and snifs him all over to get good lock on his scent. "Worry not, he will not harm you." Kazri informs. Then something occurs to her, and she goes to Vellynne and whispers to her ears. "Ms Harpell, does it mean that this gentleman here might be the only Netherese alive in the realm?"

(In case we need to search for this Xerophon, hopefully that give Oli an advantage.)

As soon as Vellynne finishes explaining things, Rhogar clicks his tongue and shakes his head. "While I can certainly a use for such magic to perserve the dying, or protect something of great import, to have done so merely as merely an experiment is.... I can think of fewer things crueler than that." He commented on heatedly as a few sparks of electricity crackled briefly along his scales.

After a minute or so of not so quietly fuming over the actions of the lich/demilich, Rhogar's expression however softened upon looking again to Xerophon. "For what little it may matter to you in this moment, you have our condolences, and our most sincere apologies for bearing little in the way of good news. If you feel you need time to rest and process at least most of what you heard, then I believe we can be accommodating on that front?" He looks uncertainly to the rest of the party. "We'd also be happy to share more of what we know of the time since... mn, everything that has happened after your sequestering. Though understand that even our knowledge and understanding will be limited." The dragonborn continued. His his eyes then went wide for a second, before then with a sheepish grin, he'd bow his head once. "Forgive the lack of decorum on our part. My name is Rhogar of Clan Nimbatuul. A dragonborn in the common tongue. Though my peoples' relationship with true dragons is... a lengthy story better suited for another time."

Krom nods in agreement to Rhogar's suggestion. "Of course, of course, since you are still probably hungry, we can all have a proper dinner and rest for a while." The dwarf then introduces himself. "I'm Krom Firebeard, Smith of Moradin."

From his spot next to the table Chill gives a grin and a quick wave.   "I'm Chill."

He gives a quick nod and then head back to the entryway. 

Before Vellynne has a chance to answer he responds himself.

"I think that is exactly what that means Kazri.  He's the last.   He could have information on their lost civilization historians might be interested in."

"We certainly could take a rest and answer any questions you might have Xerophon if you can help us as well. "

There is a slight sense of wonder from the Paladin as she looks at this person that's the only one from this ancient empire. "Yes, of course Chill... This is Oli." She pets the owlbear as he waddles back to her side.

Vellynne nods in agreement with Chill.  "Yes, the last it would seem.  So much lost information. Historians would truly be interested in spending much time speaking with you Xerophon. As for me, I am Vellynne, from the Arcane Brotherhood.  I know many a scholar and wizard who would wish to speak with you. Stay with me and I will keep you safe."

The location you are in is as safe a place as any to take a short rest.  You offer Xerophon food from your ration packs and speak with each other for a while.  Your sense of him is that he is quite overwhelmed by the knowledge that 2000 years have passed and everything he knew is now gone.  Walking to the entry to the prison he can see the devastation of the city from time and the cold as well as the fall from the sky. 

Xerophon tells you of the city.

"Ythryn was under the command of a lich named Iriolarthas. He was obsessed with finding relics and magic from Faerûn’s ancient past. He was my master. The city was governed by a group of eight arcanists known as the Wizards of the Ebon Star. As for the mythallar, the city was held aloft by the magic of an arcane sphere known as a mythallar. The mythallar also had the power to recharge magic items and control the weather. It can be found in the Spire of Iriolarthas. In times of trouble, the wizards raised a force field around the enclave’s central spire that only they could pass through. To bypass the force field around the spire one must perform the eight steps of the Rite of the Arcane Octad outside the spire. The steps of the ritual are hidden inside towers dedicated to the eight arcane schools of magic. I know the city and can lead you to each of these towers. Please let me stay with you and keep me safe.  I am sort of lost at this moment."

"So Iriolarthas was already a lich..." says Krom while scratching his chin "What about the other arcanists? Were also undead too?" asks the dwarf.

"Of course, you are welcome to stay with us Xerophon." Krom pats Xerophon on his shoulder. "Your knowledge will help us save a lot of people."

"As soon as we are ready, we should head to the nearest tower and start that ritual. I still have the strength to invoke some of Moradin's blessing, they should help us for one step or two of that ritual, but we will have to proper rest soon. We should be at our best in case of encountering Iriolarthas." says the dwarf at the rest of the group.