Onizos: 5

O stands or rather "swims" ready further back at the top of the pit. If this thing attacks his friends then he's ready to show it that it's not the only thing down here with tentacles...

Octopus Stealth: 10 (No one is surprised)
Octopus Initiative: 8

Baetrix Initiative: 18

She will act first. As she approaches the edge of the pit, she sees the giant octopus starting to charge Yabo and Gan. Without hesitation, she level her crossbow, hoping it works properly underwater.

To Hit: 12

The bolt wizzes through the water, cavitation bubbles trailing behind it. It strikes the octopus at the base of one of it's tentacles and dealing 5 damage.

Igreis is next, then the octopus.

Initiative Order:

Map:

 Both Igreis and his ehco will move forward to be close to the octopus, one readying their rapier and shield as similar but blurry shapes form with the other. As they get close both move to make an attack.

Rapier: Attack: 18 Damage: 8

Unleash Incarnation Attack: Attack: 24 Damage: 5

Igreis will then Action Surge to make another attack along with his Echo.

Rapier: Attack: 9 Damage: Unable to parse dice roll.

Unleash Incarnation Attack: 

Attack: 18 Damage: 5

Unfortunately the Rapier attacks would be at disadvantage underwater. You're welcome to retcon to a different action if you'd like, or roll again for the action surge attacks

(Well apparently I could use his dagger without disadvantage to attack underwater unfortunately it would be metagaming to switch. Sucks cause now I basically wasted my turn and special abilites if I miss....)I Now remembering why my entire table did not have much fun with a semi underwater campaign with combat....)

Disadvantage: 13

Disadvantage: 23

On his turn, Onizos goes a bit still in the water, face uncharacteristically slack and expressionless, as a sphere of dark energy appears over his head. Whiplike, a dark tendril of energy like a tentacle shoots out to lacerate the octopus

eldritch blast

18 to hit ; 8 force damage

Igreis and his echo are able to each focus on one of the tentacles, weaving through through the melee and landing one blow each.

The octopus swipes at Gan trying to dislodge him from Yabo's side

To Hit: 9

The tentacle swoops over his head.

Gan, you're up! Then Onizos

Gan looks up as the the tentacle swishes across his head.

"Stupid octopus," Gan mutters, then he opens his mouth and lets out an almost dragon like roar. "Get the hell out of our way."

He then waves his fingers at the octopus then claps his hands together in the water, while at the same time saying "führungsbolzen".

Electrical energy crackles around, causing small bubbles to appear around his hands. Then a bolt of light flashes through the water, lashing out at the octopus.

Bonus Action - Draconic Cry - As a bonus action, you let out a cry at enemies within 10 ft. of you. Until the start of your next turn, you and your allies have advantage on attack rolls against the enemies that could hear you.

Action - Casts Guiding Bolt - Attack: 25 Damage: 32  radiant damage.

Onizos's move and rolls are already above, but I suppose there's a chance to crit

Second attack roll to see if there's a crit: 4

The Octopus recoils under the magical barrage from Gan and Onizos. Blood starts to cloud around gashes across it's body.

Yabo is up

Yabo kicks down, and slashes at the octopus with his claws.

Attack: 11 Damage: 9

(Everyone has advantage on attacks against the octopus until Gan's next turn).

((Ah, I didn't read the cry well enough, I was just thinking that there was advantage from the guiding bolt.))

Attack: 18

The octopus's eyes widen as your claws rip into it. It's starting to flail about fearfully.

Baetrix takes another shot from the lip of the pit.

To Hit: 19
Damage: 9

Just as the octopus was preparing to jet away, the bolt strikes it in it's eye and it settles lifelessly back down into the sand.

Combat's ended

Already nearby, Yabo will swim down and investigate the glinting thing that drew them close.

At the bottom of the pit, you find a significant amount of silver coins scattered about. You're able to scoop up 57sp. In the small leather pouch you also saw, you find only 8 small, porous looking pellets.

He stows the silver for now and swims back up, giving a shrug to the others, and hands the pouch of pellets to Gan. He'll point a claw in the direction they were headed before getting sidetracked.

Onizos cracks a grin, the orb of dark energy over his head winks out, and he continues on with his companions.

Gan looks at the pellets for a moment before once again grabbing hold of Yabo's shell and swimming along behind.

"I couldn't help but notice you's gots the silver and I got small rocks," Gan mutters as they continue along.

But then he thinks, maybe they're valuable, or better yet, magical. He'll have to check them when they finish the race.

Yabo twists his head back to look over his shoulder and shrugs, not really having a way of telling the kobold that he'll get a cut later, since he isn't able to speak while holding his breath.