Advanced Adventures #2: The Red Mausoleum is a short adventure designed for 6 to 8 characters of levels 12 to 15. Written using OSRIC (the Old School Reference and Index Compilation), it is largely compatible with Advanced Dungeons & Dragons 1st edition. From the publisher's website:

The populated regions north of the Sister-moors have enjoyed over a century of respite from the wars that once plagued the area. However, within the past year, baronial patrols have reported clashes with undead and other dark creatures brave enough to strike out from the moors into the forests of men and elves. The Baron's sage suspects that the undead issue out of the mysterious ancient landmark known as the Red Mausoleum located somewhere on the wild stretches of the moors!