Just for clarification: There are five doors to the north. We'll label them (from left) A, B, C, D, E.

A - ?
B - Qivys got a glimpse of something quite big with green scales and black hair, moving uneasily. It did not respond to his telepathic entreaties.
C - The cell containing the giant eel corpse with the partially-blocked passage behind.
D - Evidently contains a raspy-voiced entity. (Boko got enough of a glimpse through the crack to verify that it's another cell, but not its contents.)
E - Borgas' cell.

There is one closed door to the south. Bokotopus heard muted sounds of many distant voices shouting, like the roar of a crowd, some distance beyond it. Borgas described the maze of hallways beyond it, one leading to the guard chamber and then the barracks and exit.

Peri:

"Who's that?" calls a raspy voice from inside the next cell over.

Peri drifts over to the cell door and answers, "No friends of the sahuagin. Who're you?"

Kei 

"Ooh, we have something behind door number four!" His attention momentarily taken away from what appears to be their only exit. "You found a friend?" he joins Peri at the door with a voice beyond its closed portal.

"I am Kysh!" calls the raspy voice. "Soldier and diplomat of the Citadel of Ten Thousand Pearls. Where am I? What is this place? Who are you?"

Meanwhile, Borgas continues to mourn his eel friend.

Qivys remains in the center of the room, ((per 6796), watching the exchanges and waits.

Gerrard:

Moving with Borgas, Gerrard says softly, “I am sorry for your loss. Your companion was dead before we arrived—yet another victim of the merciless sea devils—and the ropes you see allowed us to enter here past his body.”

”Even in death, he thwarts the sea devils, for his body conceals the hidden entry by which we arrived,” he says, adding, “But in order to defeat the Sahuagin before they hurt others, we must be smart and patient, learning all we can about their lair and leaving unnoticed that we may return with a greater force to eradicate them.”

Gerrard’s fist clenches as he continues speaking, obviously thinking of his own allies who have been injured by the sea devils, not just the eel before him.

“What do you know of the other captives here?” asks Gerrard.

Gerrard:

History on the Citadel of Ten Thousand Pearls:  15

Boko also listens and tries to think of what she knows about the Citadel: 18

Borgas remains quiet. Then he finally replies quietly to Gerrard, "I know nothing of them."

Neither Gerrard nor Boko has heard of the place Kysh named from behind his cell door.

Gerrard:

Shrugging, Gerrard says, “I see no reason not to release whatever prisoners the sea devils may be keeping here, this Kysh included.”  He moves to lift the bar to Kysh’s cell unless someone else intervenes.

He then offers to hand the crossbow and case of bolts to Borgas and says, “You can have this, or I have a spear in my bag if you would rather have that.  We should get moving soon.”

Qivys moves to stop Gerrard, placing his hand on Gerrard's shoulder.
"Not yet lad." he tells the young noble. 

"So" Qivys says to the prisoner. "Yer a Soldier an' a Diplomat eh? So was ya here servin' as a aid ta tha Sahaugin or was ya negotiatin' with 'em fer yer king?" he asks. 

Qivys interrogates the raspy-voiced captive behind the door.

"The sahuagin?" replies the voice. "No. Are you sahuagin? I was struck from behind by assailants unknown, and I don't know what happened next. Where is my sea lion companion? And I ask again, who are you? Why am I being locked up here?"

"I have no idea why yer locked up in here." Qivys replies. "An' I don't know where yer companion is." 
Qivys thinks for a moment.
"But yer stuck in what we believe is a Sahaugin prison an' we" Qivys continues. "appear ta be freein' prisoners."  Qivys looks at his companions out of the corner of his eye. 

Peri:

Peri is alarmed at Gerrard's move to open the cell, but fortunately Qivys stops him. Just because the Eels don't like him doesn't me we should. He thinks Kysh's explanation sounds a little fishy -- "hit from behind by assailants unknown?" "You'll have to forgive us, but we're none of us from the sea, so we don't know anythin' about the Court of a Thousand Pearls." As he says this he looks to Kei and nods toward Oceanus, hoping to convey "ask the sea elf" with his gesture. (Insight check while Kysh answers, to try to determine if he's lying: 15)

((I'm not a bit sorry for the pun.))

((Edit: Halfling luck on that check = 21))

"The Citadel of Ten Thousand Pearls. The Sea of Light. Her majesty, the Mother of Foam!" intones Kysh from behind the door. "I am one of her humble emissaries." 

Oceanus gives a tentative nod and makes an uncertain face. He adds in Elvish:

 Peri senses no lying here, although it's hard to be certain, especially without seeing Kysh's face or body.

"Tha elemental whatsit?" Qivys says with a puzzled look on his face.
Qivys shrugs his shoulders. "What ever." he says quickly "We freein' this one as well or are we headin' ta do what we came ta do?" he asks. 

Peri:

He shakes his head to Dwal, still not sure which side this courtier may be on, or whether releasing them would be a mistake. "Again, I wish to give no offense -- we're all air-breathers, and to be honest I couldn't tell one court from another on dry land. So tell me, who were you emissaryin' to? And what's your court's relations with the sahuagin like?"

"I'm not here as an emissary," replies Kysh from inside his cell. "But rather as a scout. There is talk of a portal, a rift of some kind, somewhere near the coast, a leak out of the dark planes. Do you know of it? I had no intentions of interacting with sahuagin, with whom we have no relations."

Boko spins around, her octopus head aimed right at Kysh’s cell door, eyes intent and interested as soon as he mentions a rift leaking elements from the dark planes. She shivers, as much as an octopus can shiver.

Gerrard:

His face going pale, Gerrard considers the implications and whispers to Kei, “Could it be? Peleg’s tower?”