Wizards of the Coast released this as a free 71 page downloadable pdf, and as a commercial release 96 page softcover. The two versions may differ slightly in content.
A D&D adventure for characters of levels 1-3.
The town of Winterhaven stands watch over a ruined keep that was once a bastion of good in the realm. This keep overlooks the Shadow Rift, a dark scar in the world that was once a gateway to the Shadowfell but has been dormant for many years. Now, an evil cleric of Orcus, Demon Lord of the Undead, seeks to re-open the gate, and the only thing standing in his way is a small yet determined band of heroes from Winterhaven.
Keep on the Shadowfell is an exciting Dungeons & Dragons adventure designed for characters of levels 1-3. It includes three double-sided poster maps suitable for use with D&D miniatures, as well as information on the town of Winterhaven and environs.