Struggling against the surging waters, Kellen manages to get as far as the edge of the tunnel before lighting it up. The tentacled horror is suddenly illuminated in horrible detail from behind as it grasps Gerrard. 

Gerrard struggles, sinking his blades again and again into the horror holding him hostage. Then Gerrard goes limp.

The creature releases Gerrard, before disengaging and swimming forty feet further down the tunnel, out of sight once again.  

"A truce, then," whispers the voice in Gerrard's head. "I will not harm you. I will answer your questions."

Gerrard and Kei: Make an Intelligence save.

Gerrard Intelligence Save:  3

Edited to try and push through the roll….

Kei 

INT save 14

A light flickers on, deeper down the tunnel, beyond where Kellen is able to see, beyond where his eerie orbs of white light penetrate the gloom.

A vast cavern lay ahead. At least four more of the tentacled horrors peer into the mouth of the tunnel from the other end.

"Help us," whispers the buzzing voice in your heads. "Help us defeat the invaders. Help us save the Styes. Help us save Seaton. And the other inhabitations of this coast. There are two of them. Two beings which seek to destroy everything. Help us defeat them."

Kellen

Unable to see any further, but not willing to go further down the tunnel, Kellen tries to peer through the gloom, launching a wisp of light at where he thinks the Whisperer is.

Attack at disadvantage: 24

Damage: 14 radiant

He also sees the fools that dove in are wounded, so he opens his mouth to speak soothing words, though only bubbles come out.

Gerrard: 9 hp regained

Kei: 10 hp regained

The creature, at the far edge of Kellen's range, gasps in pain and anger as Kellen lights it up.

"Suicidal, brainless, fools..." 

Kei tenses again in pain. (Kei: take 14 psychic damage.)

Kei and (if Kei has released him) Gerrard may act next.

Kei 

When a soft mote of light slips by his shoulder and strikes the creature Kei again winces in pain. He let's out a groan followed by a plea, "Stop attacking it, please!" The pain so intense this time it breaks his concentration on his magic. Knowing that Gerrard will soon be on the assault again, Kei moves to intercept his friend before he can cause the aboleth,  and by association himself, any more pain. He moves up to Gerrard and looks at him directly in the eyes. "You need to trust this creature. At the very least, you must stop hurting it."

Persuasion 17

Gerrard:

”These creatures speak into our minds and have fooled many.  It has already infected me like Mister Dory.  Prove to me you are not under its influence and I will stop,” he grunts out through the water breathing spell.

Insight:  12

Unless Gerrard intuits something that makes him confident he should stop attacking the aquatic horror, he will move and dash to get back adjacent to it.

Fools! 

The tentacles reach out toward Gerrard once again – not to grapple him, but rather to tear his limbs off:
Tentacle Attack #1 vs. Gerrard: 27. Hit: 14 bludgeoning damage.
Tentacle Attack #2 vs. Gerrard: 10. Hit: 13 bludgeoning damage.
Tentacle Attack #3 vs. Gerrard: 21. Hit: 12 bludgeoning damage.

Then it retreats once again, another forty feet, but this time more recklessly. (Gerrard may have an opportunity attack as it does so.)

(Gerrard intuits nothing from the creature – this entity is perhaps the most alien being Gerrard has ever encountered. It is nearly impossible to read. As to Kei, he seems distracted and uneasy.)

Gerrard:

Gerrard is unable to dodge the first and third, but he avoids the second.  He then strikes as the creature flees!

Scalding Dagger:  Attack: 15 Damage: 13

Gerrard:

Following to the edge of the opening into the larger chamber, Gerrard stays within the hall and assesses his chances.  By himself, with a swarm of creatures out there, he has little chance.  Taking up a defensive stance (Dodge)within the questionable protection of the hall, the young noble says, "Are none of you with me?" to his companions, "These creatures feast on the feckless cultists and have corrupted my very flesh!"

Quote from cbaer8 >>

(Gerrard intuits nothing from the creature – this entity is perhaps the most alien being Gerrard has ever encountered. It is nearly impossible to read. As to Kei, he seems distracted and uneasy.)

 (Gerrard was trying to intuit Kei's argument, not the aboleth directly.  Hoping with the insight >  persuasion he might learn something).

Gerrard's burning blade drives deep into the alien horror. Still lit from Kellan's starry wisp, it retreats into the cavern, trailing unearthly gore behind it. Its companions cry out.

Then, suddenly, the companions are gone, and the cavern is gone. The waters go still. The starry glow begins to flicker out. You can see nothing but endless tunnel ahead, lit up by the creature's arcane glow. It goes still and quiet, staring at you forty feet beyond Gerrard.

Everyone may act.

Gerrard:

”See, even now it tries to deceive us!” says Gerrard, plunging forward and dashing to get up adjacent to the creature.  “No more tricks or I kill you right here, right now!” he yells at the creature.

Intimidation:  25

Kellen

Closing his eyes briefly, as if preparing himself, Kellen vanishes in a cloud of bubbles, reappearing a split second later at the last orb of light in the tunnel. He fires off another wisp of light towards the horror:

Attack: 20

Damage: 16

Kei 

Kei braces as he sees Gerrard plunge his steaming dagger into the creature. But no pain comes. Relieved, Kei follows Gerrard but only to within 15ft. Passing the newcomer and paying them no attention he mutters a string of bubbley words and three inky black shadow slivers fly from his outstretched hand. "I truly am sorry Gerrard" he says hoping the noble can hear his apology. Before the air expelled with his apology can reach the roof of the tunnel Kei twists his hands downward then raises them slowly, a scene Gerrard has seen before. A twisting tendril of shadow rises from the tunnel floor. The tentacle lashes out.

Attacks made against the creature. Rolls in game log to avoid manipulation tag.

Kellen's magical lighting upon the creature fades. Arcanely closing the distance, he fires a fresh starry wisp at the motionless horror.

Kei likewise advances, blasting the creature with a trio of crackling black beams. All three hit, tearing into the creature, as does his inky arcane tentacle.

Gerrard examines the newly glowing form. Torn open and motionless, it appears to be quite dead.

Gerrard:

Swimming forward to check out the form, Gerrard says through the magic of water breathing, ”So this was the Whisperer.  To be honest, I don’t know what to believe—that it was an evil creature bent on deluding us, or that its warnings about bigger threats to the city were in earnest.  Still, it lured citizens to this den to die and be eaten, so it can’t have been truly altruistic.”

Looking at his body to see if the transformation effects fade with the death of the Aboleth, Gerrard says, “What do you think, Master Kei?  It seemed to be influencing you somehow right up until its death.”

Turning to the newcomer, he adds, “Thank you for your aid.  I am Gerrard Feldren, champion of lost causes, it would seem.”

Kei 

"Not completely. It did have hold of me for the most part. It tried to make a friend of me, by force. It knew things, desires, and used that against me. Although it did use me as a healing potion too, draining my life force as you damaged it" Kei replies as he approaches the now dead aboleth. "It let me go just after the others disappeared. I'm sorry if i put you in harms way, it was too difficult to refuse its commands". 

Eyeing the newcomer with suspicion Kei gets as close to Gerrard as possible before whispering (possible underwater? ) "I know it's name and that of the two it feared, perhaps that will reveal something more".