The Crystal Coffins

From publisher blurb: A Swords & Wizardry Mini-Dungeon For 4-6 Adventurers of Levels 5-7 The ghost of a necromancer is raising an army of undead. He can only be stopped by destroying his earthly remains, hidden in a crypt guarded by eight crystal coffins. Unfortunately, the coffins are guarded as well... The Crystal Coffins is part of a series of mini-dungeons designed to drop into existing adventures or campaigns. Use them as side quests or a way of getting in a quick adventure when you’re short on time.