This post contains the remixes and changes I used for the Lake Monster quest picked up in the town of Bremen in Icewind Dale: Rime of the Frostmaiden. It runs similarly to what is written in the module with a different backstory, delivery and climax. You can likely use this remix as an independent encounter in any game, but to get the most out of it you will need the module.
Remixes have become a great way for DMs to talk about how they are using published content in the wild for their actual 5th edition games. It focuses on how you arrange or change the elements to suit your individual game and style, and avoids the o-so-very-internet thing of labeling things as broken or awesome.
An NPC I fleshed out for my Icewind Dale: Rime of the Frostmaiden campaign. She is the silent and secretive leader of The Harpers in Icewind dale, dedicated to keeping the faction members safe in the wake of assassinations years ago.
A ramshackle and squat two story stone building made held together by rotting timbers, with opaque frosted windows and a dilapidated tiled roof. It sits on a side road along the edge of town slightly northeast of the road to Targos. This is a standard 25x25 battlemap I created for my Rime of the Frostmaiden camapgin, I hope you can use it too.