The Pit in the Forest

From the publishers blurb: In Claine Forest near Padduck Village there has appeared a pit. No-one knows where it came from, it just did. It is not so deep that you cannot see the bottom, but people fear it and avoid it. No-one who has climbed into it has come back, having been dragged beneath the surface by unseen hands. A necromancer has come to the forest, seeking the pit. She does not quite know what she expects from it, but what she hopes for is protection from death. Player-characters may wish to get involved, and thus this constitutes an adventure for old-school systems, for 5-6 PCs of 2nd level 2 or slightly fewer of 3rd. The PCs won’t necessarily all die, and the players will almost certainly survive.