Hi! It's not written for 1e but the only change needed is to convert the Frost Wretch stats to 1e stats using the Conversion Kit from the Kickstarter. I would just reduce the stats by around 5-10 points across the board to keep it dangerous. Other than that, no conversion needed!
Also, I plan to republish this as a 1e module sometime in the future. But there won't be any other changes than the aforementioned + the 1e compatibility logo.