Life is a Lonely Business

From the Introduction: Life Is a Lonely Business is a standalone encounter designed for five 15th to 17th-level adventurers. In an attempt to solve the puzzle of life and death, a cleric named Alfrenk has breached the thin wall of the Shadowfell, inadvertently releasing ravenous wraiths and restless ghosts. The players must defeat the spirits in both the living realm and the Shadowfell, passing between the two planes during combat.