So I've seen a few posts about good ways to lead into creeping fog, so I wrote up a short intro to make it feel more natural and give my party a chance to grab some supplies before the appropriately named Death House:

The party starts in an inn, brought there because of a help wanted poster. A man is putting together a search party funded by a rich family in order to find their missing children, Worgs have been acting strange around the town recently so the man leading the party doesn't expect a happy outcome, but they're paying very well. The party gets a lump some of gold (I'm giving them 100 gold, it seems like a good amount because I'm hoping they buy some healing pots) up front in order to purchase supplies, and is given a backpack with basic camping supplies, the party is joined by three other adventurers and are given time to shop around time before leaving early the night morning.

The next day the group ventures deep into the woods, following worg trails from the family's house where the kids were last seen playing until they find a bunch of strange tracks (including the children's) but quickly loses them which causes the NPCs to split off and search around to regain the trail. The party hears screaming and growling and races towards it, only to find the mangled corpse of one of the other search party members ( If my party decides to check the corpse I'm going to have it made clear that the worg wasn't hunting him for food, and it seems more like a brutal murder) The search party leader then buries what's left of the corpse before the camp stops to rest, the trail having gone cold again.

While the party is asleep I plan to DM them all a nightmare they had, I'm going to send the same nightmare to each of them to see if they end up finding out they had the same nightmare. This part I don't have down quite yet, maybe figures following them through deep, unending fog perhaps?

The party is awoken in the middle of the night by howling, growling, and the rest of the search party yelling and fighting a short distance away. As the party runs to help into the deep, dark forest, a thick fog closes in around each of them.

If you made it this far, thanks for reading! I'd appreciate any feedback and anyone is welcome to use this as a way to more naturally lead into creeping fog besides "You fall asleep and awake in a new place."