Shipwrecked in Saltmarsh

The robed figure (whom Molo just learns is named Krell) dodges more tentacles and tries to dash up the stairs:
Krell DC10 save vs. tentacles: 15 
...he deftly evades them. Running up the listing stairs: DC10 check: 17
...he successfully ascends and then ducks past Katernin. He is now in the cabin above, near Dain, where he holds up his stick, preparing to strike Dain.

(Katernin may get in an attack of opportunity as he passed her at the top of the stairway.)

 Katernin, Molo, and Kelnan may act next. A horde of monsters prepares to run up the stairs toward Katernin. (Start with your dex save!)

 Katernin, Molo, and Kelnan are up next. Katernin also has an opportunity attack she may make on the robed figure.

- Kelnan is on the top deck. He sees Fianna's plight.
- Molo is being carried by Dain, still reading Krell's thoughts.
- Katernin is at the top of the stairs, still sporting mystical, translucent wings. She sees a horde of spiders and horrid mouthy demons preparing to storm up the stairway in her direction. The robed figure ("Krell" Molo knows) just brushed past her, racing for the exit.

• Remember that everyone must start their turn with a DC10 Dex roll or take 2d6 bludgeoning damage from the thrashing tentacles.
• Remember that the 30° tilted deck is Difficult Terrain. Half-speed, essentially. (It tilts to port, toward the tentacles.)

Molo Dex save 11 

 Molo avoids the tentacle from Dain’s protective arms and attempts to delve further into Krell’s mind to find out what might make him open to the idea of a trade: getting the box for us. 

In the midst of all this chaos, Molo can only focus on the box

(Just realized I never gave Krell a saving throw. Here it is: DC14 Wisdom Save: 16 )

 Krell's mind closes to Molo's further attempts to read it. Molo may have a new action if he wants.

Molo will attempt to jump in after the box

Kelnan

Dex check: 23 (Advantage from Cursed Luckstone)

Deftly avoiding the smashing tentacles, Kelnan looks back at the party remaining onboard, then down at the churning water beneath.

Certain death, or only somewhat likely death?

He uses Misty Step to place himself in proximity to Fianna and the sinking chest and hangs on with all his limited might.

Molo, shut out of Krell's mind, slips out of Dain's grip and hobbles toward the railing. But between his bad foot and the sloped and shuttering deck, he is barely able to get ten feet. 

Kelnan vanishes into a cloud of silvery mist and appears in the water next to Fianna to grab hold of the bulky, heavy box. (Even with two of you holding it, together with Fi'Finella and a Mage Hand, next turn one of you must succeed on a DC 10 Strength (Athletics) check at the start of the shared turn while the other character uses the Help action to give the roll advantage, or both characters will sink 20 feet.)

Katernin may act next. She is at the top of the stairs, still sporting her wings, where she sees a horde of spiders and horrid mouthy demons preparing to storm up the stairway in her direction. Krell has just brushed past her, racing for the exit; she has an opportunity attack available against him if she wishes to use it. (As always, remember to start your turn with a DC10 Dex roll or take 2d6 bludgeoning damage from the thrashing tentacles.)

(Well we both have an 8 for strength so not much difference who helps and who rolls…)

Kelnan

(I'm loving the image of two weenies struggling with a huge chest in the water)

Athletics: 16

I'll hold on Kelnan and Fianna's fortuitous roll until the top of the round. Katernin (and the horde) will finish out this round.

Initiative recap:

√ Fi'Finella
√ Dain
√ Fianna
√ (Krell)
   Katernin
√ Molo
√ Kelnan
   Giant Spiders
   Mouthy Demons

Katernin swings her handaxe at the fleeing figure:
Handaxe melee attack vs. Krell: 6. Hit: 3 slashing damage.

...but the strange figure is too fast for her.
She attempts to dodge the everpresent tentacles which continue to tear up (and tear holes in) the ship:
Katernin DC10 Dex Save: 0 
But fails... One clobbers her right leg, doing 2 bludgeoning damage.

(I already deducted it from your sheet; bringing her to 19hp.)

On her ghostly wings, Katernin dashes circuitously around the mast (to avoid the mysterious staff-wielding figure), and diving past Dain, flies nearly to the railing. She can see Kelnan, Fianna, and Fi'Finella struggling in the black swells below.

The horde of spiders and demons attempt to climb the stairs while avoiding the tentacles:
Spider 1: DC10 Dex Save: 4. DC10 Strength check: 12
Spider 2: DC10 Dex Save: 5. DC10 Strength check: 5 

...due to their climbing abilities, both succeed in climbing upstairs, but one takes 9 and the other 11 in damage from the tentacles. They dash up the tilted deck, stopping behind Krell and unable to yet attack.

The first two demons are right behind them attempting to climb the stairs, and more are at the bottom of the stairwell:
Demon 1: DC10 Dex Save: 9. DC10 Strength check: 16
Demon 2: DC10 Dex Save: 3. DC10 Strength check: 21
Demon 3: DC10 Dex Save: 14.
Demon 4: DC10 Dex Save: 12. 

The first two demons succeed in climbing most of the way up the stairs, but one takes 5 and the other 2 in damage from the tentacles. 

The waves begin to break over the port deck, and the massive black-green tentacles continue to thrash. The deck below is almost completely flooded. The dwarves are rowing to your rescue, but they are still many rounds away.

Kelnan, Fianna, Fi'Finella, and the mage hand continue to (barely) keep the box from sinking for another round. (That is their action this turn, already fortuitously rolled by Kelnan.)

Dain, still in the doorway facing Krell and his horde, may act next. 

√ Fi'Finella
   Dain
√ Fianna
   (Krell)
   Katernin
   Molo
√ Kelnan
   Giant Spiders
   Mouthy Demons

Dain

Dain attack's Krell in order to delay the mob so that Molo and the others can get off the ship hopefully secure the box.

Maul Attack: 11 Damage: 11

(Thought about grabbing Molo and throwing him but seemed too LotR to me...)

Dain stands in the doorway and prepares for the onslaught. His maul slides harmlessly off the figure – whatever Krell is, he has abnormally tough skin, as he appears to wear no armor over or under his robes.

Krell responds with a two-handed thwack of his quarterstaff:
Quarterstaff attack vs Dain: 16.  Bludgeoning damage: 6 
"Go! Get out of the way, you stupid pig!" he shouts thickly, in heavily accented Common.

The quarterstaff bounces off Dain without injury.

Meanwhile, both dodge more swiping tentacles:
Dain DC 10 Dex Save: 3 or take 7 bludgeoning damage
Krell DC 10 Dex Save: 2 or take 10 bludgeoning damage

 Dain easily dodges them, but Krell takes a nasty, cracking blow to his ribs from behind. He is battered but still standing, and focused sharply on getting past Dain.

Katernin and Molo are up next! (Molo can hobble 5' per turn on the slanted deck; 10' if he dashes.)

Molo is still headed for the item that fell in the ocean

"Dain let's go," Katernin calls out, reaching out with the last bit of divine power she does have to shield him so he can run. She then turns to fly out towards the dwarf boats to help them.

Bonus Action: Cast Shield of Faith on Dain

Action: Dash towards the Dwarf boats.

Katernin casts a shimmering field of protective radiant energy around Dain as she flies off on her wings before the tentacles can grasp her. She dashes through the air toward the skiff, which is still some 170 feet away. The two dwarf sailors are rowing as fast as they can toward Fianna and Kelnan, but they are still eight or nine rounds away from arrival. Katernin realizes that her wings will disappear soon - in about three rounds. She should be able to get to the skiff, but not back again.

Molo continues to dodge the everpresent tentacles: DC10 Dex Save: 21 or take 7 bludgeoning damage.

Easily evading the blindly thrashing appendages, Molo hobbles up the steeply-sloping (and lurching) deck as fast as he can Dash. He is nearly to the rail (just five feet away) and will be able to dive into the water next turn.

The horde of spiders and demons attempts to dodge the battering tentacles:
Spider 1: DC10 Dex Save:  23
Spider 2: DC10 Dex Save:  9
Demon 1: DC10 Dex Save:  0
Demon 2: DC10 Dex Save:  18
Demon 3: DC10 Dex Save:  8
Demon 4: DC10 Dex Save:  0

Two more demons attempt to climb the stairs:
Demon 3: DC10 Strength check:  21
Demon 4: DC10 Strength check:  21

One of the demons slips and falls back down the stairs into the flooded lower deck. The two spiders and one demon are slammed by the crusty tentacles, taking: 6, 5, and 11, respectively.

Both spiders are crushed to pulp, but the mouthy demons swarm around Krell and Dain.  

Two attack Krell, one attacks Dain:
Demon Bite Attack #1 vs. Krell: 6  Hit: 8 piercing damage.
Demon Bite Attack #2 vs. Krell: 6  Hit: 10 piercing damage.
Demon Bite Attack #3 vs. Dain: 6  Hit: 4 piercing damage.

 Dain holds off his attacker, but Krell goes down with a horrible wail as these unearthly creatures begin to devour him.

-- Top of the round --

The waves breaker a little higher on the port side, as the distant skiff gets marginally closer. 

Fianna, Kelnan, Fi'Finella and a Mage Hand must succeed on a single DC 10 Strength (Athletics) check on your shared turn while the other character uses the Help action to give the roll advantage, or both characters will sink 20 feet.)

Dain and Fianna are up first.

DAIN

Dex Save vs tentacles: 18

     Shaken but not tossed by the tentacles, Dain sees the numbers getting bad for him quickly.  And the way that wizard was taken down, he is anxious to skedaddle!  Seeing everyone is off the ship except for Molo, and feeling the extra protection from Katernin...  Dain decides to risk turning his back on his enemies and run for it!

     Dain shouts out "Come with me!" to Molo as he turns and runs after the Kobold.  Slowing just enough to pick up his companion, Dain will continue running towards the edge of the deck, looking to jump overboard and carry them both into the water...  ((Will use movement and dash if picking up Molo doesn't take an action?  DM's call...))