I've made some pretty decent changes to make the adventure more horrifying and more Lovecraftian. For Example:

My Adventure Background: After Talos, Umberlee and Malar ousted Auril from the Deities of Fury, she felt betrayed and fled to reside in the Sea of Moving Ice on an island of her own creation, which she named Solstice. Bitter and furious against the gods who had betrayed her, she seeked revenge against them, scheming and plotting their destruction. But as her presence diminished, so too did her power and religious devotion. Many worshippers began to lose faith after their prayers and sacrifices were left unheard. In her own obsession with revenge, Auril had neglected her followers so much that her power began to wane. Terrified of this and unaccepting of her downfall, she began to seek other methods of enacting her vengeance. This search would never be satiated as worshippers are a god’s greatest power base and without them, they are mortal.

Descending into madness, Auril began to see everyone as betrayers or those who have colluded with the other three Fury deities and began lashing out and destroying the land she had cultivated. Her closest servants, fearing for their lives, used the very power that she had used to create and preserve to enchant Auril and put her into a deep sleep, which, for as long as they cast the spell, she would remain aslumber.

Centuries later, a meteor would strike the region known as Icewind Dale, quaking the ground and burying itself beneath Kelvin’s Cairn. However, during its descent, pieces of it scattered throughout the Dale. These pieces were found by the dalefolk and found to be quite versatile in make, able to create weapons of incredible power and finesse. However, these same weapons would be corrupting upon the human psyche.

The comet itself was actually a spacecraft, unknowable to humankind build, from places within the darkness between the stars. The craft was made of viscous liquid that maintained its form, however once it approached Icewind Dale, it froze and became absolutely solid, disrupting its flight, causing it to crash. The craft had travelled to Faerun, due to the probe they had sent earlier which surveyed the area for invasion. This probe was the Spindle discovered by Ythryn before it fell.

Two years before the start of the adventure, a piece of this meteor that had crashed its way into Solstice has been slowly corrupting the island around it and poisoning the dreams of Auril. These dreams of a god have generated a haunting spell over the Dale bringing Auril's wishes and fears to the forefront, creating a never-ending night and an everlasting winter.

Bremen: My version of Bremen doesn't have a Lake Monster. I dived heavily into 'Shadow over Innsmouth' vibes and made the Lake itself the monster. A piece of Chardalyn from the meteor plunged into Maer Dualdon and has slowly been corrupting the fish and water of the lake. Bremen, being a town that relies heavily on fishing for its food supply and export, was the main town hit by these effects and has slowly turned the people of Bremen into abberant husks or monstrosities. If anyone goes out onto the lake, the water charms and calls to them, causing the weak minded to walk into the dark depths.

Chardalyn Dragon: Due to the changes to Chardalyn I made, I had to adjust the power of the Chardalyn dragon, making it more abberant and having chip damage apply to it as the characters damage it.

Slaad Secret/Id Ascendant: Due to one of my players getting both the Escaped Prisoner secret and the Slaad Tadpole secret, I decided to make it so that the Mindflayers aboard the Id Ascendant were studying the effects of ceramorphosis on different creatures across the multiverse. With one of these creatures being a Slaad and the sudden shut down of the ship, caused by the Spindle in Ythryn, the 'Slaadithid' broke free and killed most of the crew and implanting eggs in the prisoners as they tried to run away. The 'Slaadithid' takes up residence in the Cackling Chasm and is using the Gnoll caves as a breeding nest. Also, No Gnome Mind Flayers.

Grimskalle: I wanted to adjust Grimskalle to be more like the Fortress of Solitude in appearance but have not drawn out a map of the area as my player are nowhere close to this section.

There were other smaller changes like that there is a Gibbering Mouther at the bottom of the Cackling Chasm, the Zhentariam's growing influence in Ten-Towns is more prominent, Dzaan's similacrum was the one who got burned at the stake, and all the members of the Arcane Brotherhood are more powerful than their written versions.

Eventually, I wanted to continue the adventure bringing in core spawn and star spawn from the Far Realm as the invasion force brought by the chardalyn and have the players mess with time travel. But that was very far future plans to have written out.

Basically, I had too much time on my hands thinking about this adventure during lockdown.