Regan hops down and heads toward the octopus, almost feeling bad as it pulls itself along. Just as the creature makes it to the rising water, a tentacle touches the surface. Immediately, the octopus begins to writhe and contort, its body pulsating with unnatural energy.
The octopus's tentacles elongate and thicken, its skin shifting from a dark, mottled green to a glowing, iridescent blue. The creature's eyes, previously beady and black, swell and turn a luminous yellow. As it grows, its form becomes more monstrous, with spines protruding from its limbs and a gaping maw forming where its beak once was.
The cavern fills with an eerie light as the octopus undergoes its transformation. Before the transformation can complete, Regan raises his heavy warhammer. With a mighty swing, he brings the warhammer crashing down onto the writhing octopus. The hammer strikes true, and the creature lets out a final, agonized shriek. Its body convulses violently, then goes still, the transformation halted permanently.
(Octopus takes 10 damage, and is dead)
...
Cordey puts down the mirror and forcibly releases his huge self from the entangling seaweed. As he breaks away from the gripping mess he moves himself 10' back (out of the range of the seaweed tendrils). He then readies himself for his next move.
...
Seeing that Regan is taking care of the octopus, Admiral focuses on the hag. Reaver bites deep into the hag’s flesh and, within moments, the wound begins to fester with necrotic magic.
(Hag takes 17 damage) The hag hisses at Admiral in pain and with fierce anger.
...
"Attack them you useless fools!" screams the hag to the Sahuagin. But they remain still, unsure what to do.
Seething and annoyed, the hag's skin, once smooth and radiant, begins to bubble and blister. Her eyes, which previously shimmered with ethereal beauty, turn a sickly yellow, sinking into their sockets and growing larger, giving her a crazed, monstrous look. Her hair, previously disguised as flowing and lustrous is now a tangled mass of writhing, slimy seaweed tendrils that seem themselves alive.
As her transformation continues, her mouth stretches into a grotesque, jagged maw, filled with sharp, rotting teeth. Her fingers elongate, turning into twisted, bony claws that drip with a vile, dark ichor. The very sight of her now causes an involuntary shiver to run down the spines of anyone who looks upon her.
"You will ALL pay for this!" she screeches, her voice now a guttural, echoing wail that reverberates through the cavern.
"Witness the true sight of your doom!"
As the hag's appearance becomes even more horrific, the Fossergrim, the Sahuagin guards, and the party members wrestle with paralyzing fear. Some sahuagin stagger back, unable to tear their gaze away from the monstrosity before them.
OOC:
Everyone must make a frightening sight WIS Save DC 11
[ +- ] EVERYONE MAKE FRIGHTENING SIGHT WIS SAVE
Everyone must make a DC 11 Wisdom saving throw. On a failed save your character is frightened for 1 minute.
A frightened target can repeat the saving throw at the end of each of its turns, with disadvantage if the hag is within line of sight, ending the effect on itself on a success.
With the threat of undead gone and after Moonlight is tidied, everyone enjoys a round (or two) of drink. Afterwhich, all manage to get a full long rest. The circus troupe takes Jaron up on the common room. The Whisker crew opts to lodge in their familiar quarters on the ship. Cordey and Lelay return to Cordey's lodging. 
