The tentacles tear a sizable hole in the thick hull. Planks splinter and pop. One of the bolts sinks deep into the creature, but even the oversized ballista bolt seems puny compared the enormous mass of this horror.

Gerrard: Roll a d10
Kei may act!

Gerrard:

Confusion/Madness:  9

Kei 

Kei looks on as Gerrard and Kellen exchange blows. When Kellen falls it's clear the mind control has taken a firm hold of his friends. In an attempt to put a stop to Gerrard's sword arm, Kei sends scintillating shapes coursing across the deck.

A - Casts Mind Sliver on the worm. INT17 save or take 12 psychic damage and subtract 1d4 from next save.

BA - casts Hypnotic Pattern in the area that gets both the worm and Gerrard. WIS17 save or become charmed. Utilising Quickened metamagic. 

Gerrard, still firmly gripped by this madness, slashes and swings at foes only he can see in the air. 

Kei curses the massive worm – DC17 INT Save: 14 and tries again to throw a hypnotic swirl in the air. DC17 WIS Save: 20

Gerrard may roll a DC17 WIS Save vs. Hypnosis, and also roll a fresh DC16 WIS Save to shake off this fog of confusion.

Kellen may roll his second Death Save.

Gerrard:

(That wisdom of 8 is really biting Gerrard hard this battle)

Wisdom Save versus Confusion:  1

Wisdom Save versus Hypnosis:  1

Kellen death save 2: 7

Gerrard remains confused, and is now hypnotized as well. Kellen remains unconscious on the deck and is beginning to turn a disturbing shade of blue.

The worm rears up, unperturbed by your feeble attempts to stop it. It lunges toward the bow.

Its attention becomes fixed upon Kei, as its 15' tentacles attempt to latch on to him

Tentacles Attack vs. Kei: 28. Hit: 21 bludgeoning damage plus 14 psychic damage, and Kei must succeed on a DC 18 Strength saving throw or be swallowed by the gargantuan horrid worm.

A cannon booms from under its housing atop the deck of the warship as it passes barely 20 feet forward of your drifting wreck.

Cannon Ball: 12. Hit: 43 bludgeoning damage.

The cannon misses. You can vaguely hear sailors aboard the other ship shouting in frustration.

Gerrard is incapacitated, staring into the empty sky. 

Kei should roll that Strength save, together with a Concentration check from any damage. Then he may act.

Kellen may roll his next Death Save.

(Disadvantage roll due to cloak: Tentacles Attack vs. Kei: 19 )

Gerrard:

In case he becomes free from incapacitation this round:

d10 for confusion:  10

Wisdom Save at end of round:  17

Kellen death save: 12

Kei must succeed on a DC 18 Strength saving throw or be swallowed by the gargantuan worm. (If he is swallowed, he is blinded and restrained, it has total cover against attacks and other effects outside his swallower.)

Kei should also make a DC 18 Constitution saving throw to maintain Concentration on his Hypnotic spell mollifying Gerrard (or choose to drop it.)

Kei

STR save 10

Concentration Check 11

Quote from cbaer8 >>

The grizzled first mate arrives carrying a small case, introducing himself as "Korrin". He has an unnervingly thin frame, his arms covered with skeletal tattoos. With him is a much more cheerful man bearing a full breakfast.

"Fine weather, above. Bitter cold below. The water is very deep here." He opens the case to reveal nine vials of liquid. "I'm told you may need this. Six strong healing potions. Three of water breathing, although the diving bell is prepared for you as well. Fits two."

"The wreck is upright. Some activity was sighted within it. There's evidence of recent digging." 

 

 (Should have some healing on us)

Kei is snatched off the deck and swallowed whole. His purely human strength is no match for this unearthly horror. He finds himself squeezed within rough, gooey, black walls of flesh, blinded and restrained, his body slowly and painfully being dissolved by pungent acid. He senses others here – the minds of other victims, their bodies absorbed, their intellects swirling in untethered madness.

Kei has already gathered that this creature is magically resistant (advantage against spells and other magical effects), but he realized that he has met this terrifying entity once before – back on Peleg's island prison. They barely escaped, and Gerrard was thrown into a confused state during that encounter, as well.

(Kei's concentration is broken, but not until after Gerrard's incapacitated turn.)

From deep within the creature, Kei may still act.

Kei 

With unnerving ease the creature envelopes him within its giant maw. And then...darkness. in that instant Kei's need for self preservation kicks in. Black flickering flames surround the worms head.

Inside the mouth of an ancient horror, Kei looks around. He sees nothing but can sense others. He can also feel the digestive juices if the horror beginning to eat away at his flesh. Knowing he is hurt already he decides not to attack the thing, but instead bolster his own chance for survival. A few finger and hand movements and he transforms himself into a [will seek clarification here]. He tries to force his way towards the mouth, and freedom.

R - casts Hellish Rebuke. DEX17 save or take 8 fire damage 

A - casts Polymorph on himself. Perhaps a bear, but will seek clarification on Discord.

Kei arcanely rebukes the massive worm for swallowing him. DC17 Dex Save: 16 
Restrained within the gut of this gargantuan horror, Kei expands eightfold and grows huge claws.

The digestive juices inflict 24 acid damage to Kei-Crab. 

The worm turns to face the warship. It exhales a renewed cone of Acid Breath across the vessel, killing virtually the entire crew visible abovedecks, but not before you hear their final horrible screams.

Meanwhile, Gerrard, standing alone on the deck of the wrecked ship, temporarily sees through his mental fog for a moment. (While he may not take a Bonus Action or Reaction this turn, he may choose his Action normally.)

Gerrard and Kei may act. Kellen may make a fresh Death Save.

Gerrard:

Looking down in horror at the dying body of his friend, Gerrard grabs one of the greater healing potions they were given the day before and feeds it to him.

Greater Healing:  11

With whatever movement he has remaining, he races off to attack the worm, intending to carve his way through its hide to save his other friend!

Acrobatics if he has enough movement to jump onto the worm:  28

Kei 

Concentration Check 18

Kei 

Digestive juices cover the chitinous armour of his new form. He tries to move forward but just can't break free of the muscular grip of the worms innards. Forgoing the movement he uses his new found weapon to strike at the worm from inside.

A - Claw attack 13 for 27 damage. If hit target is grappled(?) on a DC14 check