A beaded curtain extends across one side of the room. Many of the beads are precious gemstones. The strings holding the beads and gems are curiously strong, but the gems can be removed with a Strength check DC 15. When a gem is removed, 1d6 ghosts, shadows, wraiths, or wights (or similar) appear behind the curtain. They do not attack the players unless they themselves are attacked with magical weapons.
Should the players attempt to leave the room with the gemstones, the apparitions attack.
Only 1d3 of the incorporeal warriors actually exist; the rest are illusions.
Blue beads photo by Sharon McCutcheon. Unsplash License.