Shipwrecked in Saltmarsh

Kelnan fires a beam of blue-white energy at the beast:
Frost attack: 9. Cold damage: 9 

It flies wide, nearly freezing a dwarven onlooker.

*Blink* 8

Kelnan shimmers momentarily, but does not disappear.

Katernin, then Dain and Kelnan, may act next. 

Kelnan conjures up a wispy rope of flame and, after shifting about to get a clear line that won't harm his allies, throws an Aganazzar's Scorcher toward the visible spider.

12 fire damage

(Unlike Fireball, I don't think this one will ignite a wooden ship!)

Dain steps forward and swings his maul at the blue monstrosity.  "Die ye ugly scum!"  His eyes have taken on their slightly unfocused glaze that you've all become familiar with.

Bonus Action:   Enter Rage.
Action:  Recklessly power attack, twice (Extra Attack):
Attack: 19 Damage: 23
Attack: 12 Damage: 24
If either attack hits, the first one does any extra 8 radiant damage due to Divine Fury.
Note:  Dain is now granting advantage to attacks until his next turn.

Dain whirls around and sinks his maul clear through the head of the interdimensional creature, his weapon blazing with holy power. The massive beast collapses onto the deck... dead.

Dain holds his scorching spell, flames still dripping from his fingertips.

*Blink* 17

 He vanishes again. But combat is over.

Molo examines the mess of a spider for eggs. 

arcana? Nature? Same modifier 20 

     Fianna whoops in celebration and gives Dain a punch in the shoulder as a sign of a job well done!!  She then yawns and goes back to bed and to guard, wonder about the blue box…

Kelnan

While ethereal, Kelnan takes the opportunity to look about for anything suspicious or out of the ordinary, and pops back to reality near Fianna.

"For what it's worth, our patron seems to be truthful. I didn't have time to examine them, but I could see inside in a sense, and the box contains papers as we were told. They must be valuable indeed though."

Quote from nschrock >>

Molo examines the mess of a spider for eggs. 

arcana? Nature? Same modifier 20 

Molo finds no eggs, but he does recognize that large parts of the hide of this strange blue beast might be of some value.
Roll a DC15 Sleight of Hand check to successfully skin this monstrosity.

Quote from nurglich >>

Kelnan

While ethereal, Kelnan takes the opportunity to look about for anything suspicious or out of the ordinary, and pops back to reality near Fianna.

"For what it's worth, our patron seems to be truthful. I didn't have time to examine them, but I could see inside in a sense, and the box contains papers as we were told. They must be valuable indeed though."

 Kelnan spends a few more moments enjoying the strange and eerie Border Ethereal - alone this time - before returning once more to the plane of the material ship.

It is early morning. The gusty snow squalls cause the ship to lurch; the swells begin to grow; you can hear the rasp of sleet against the hull. The dwarven crew mourn what's left of their comrade.

Quote from cbaer8 >>

Quote from nschrock >>

Molo examines the mess of a spider for eggs. 

arcana? Nature? Same modifier 20 

Molo finds no eggs, but he does recognize that large parts of the hide of this strange blue beast might be of some value.
Roll a DC15 Sleight of Hand check to successfully skin this monstrosity.

 20 

Dain, back calmed once more and happy that it appears most of the threats to the ship are done, for now, will once again offer his services to the captain.

     Fianna mostly resides in her cabin resting, singing sea shanties badly, and spying on the crew and all with her invisible imp.  It's not particularly fun or interesting but there is little else to do on a ship until someone invents cell phones...

Kelnan spends the time trying to help out on the ship, probably more useful for Mending things than for physical labor. He also talks with the rest of the party about how to compensate the captain and crew for doing way more than providing a ride. Maybe give the captain an equal share to the rest of us to distribute as he wants?

Katernin also helps on the ship, feeling like she's been nothing but dead weight most of the time they were onboard.

A grim day passes as they make slow progress northwest in the snow squalls. There is very limited visibility in the gusty snow and sleet, as the captain navigates through heavy swells by dead reckoning. The captain, while satisfied by the death of the spider, is in a foul mood.

Molo manages to remove a quite sizable - and likely saleable - piece of blue spider hide. But it takes half a dozen of you to move the spider's remains to a place where the cargo crane can winch it up, out, and overboard.

As night begins to fall, Fianna's sea shanties, while quietly entertaining to the crew, takes a weird turn. As suddenly there is another voice (and a far superior singer) coming from somewhere overhead. The vessel begins to make a new turn to the east, and to noticeably heel in the strong winds outside.

Everyone should now make a DC 11 Wisdom saving throw...

Kelnan

Wisdom: 21

With advantage if a charm effect: 9

Fianna Wisdom: 9

Oh yeah, Fianna gets advantage on Charm too, if it is that - 8 and cannot be put to sleep by magic

Well, that certainly didn't help!

...

Molo wisdom save 18 

More Wisdom saves:

Katernin: 21
Dain: 18

Shouts are heard above deck. A sudden lurch sends everyone flying, together with a sickening scrape - the ship has hit something hard in the waning light and heavy sleet, and it is now leaning at a concerning angle to port. Has the ship run aground?

The strange, beautiful singing - from many voices outside the ship - continues a haunting melody. 

Fianna and Dain are incapacitated but are drawn upstairs onto the outer deck, enchanted by the mysterious song.

Initiative: 
Fianna: 5.  (Incapacitated but must move upstairs.)
Katernin: 11
Kelnan: 18
Molo: 21. (Incapacitated but must move upstairs.)
Dain:  3