This necklace is a heavy chain with a platinum medallion.

The magic of the necklace wraps the wearer in a shell of fresh air, making him immune to all harmful vapors and gases (such as cloudkill and stinking cloud effects, as well as inhaled poisons) and allowing him to breathe, even underwater or in a vacuum.

Prerequisites: Craft Wondrous Item, alter self.
Cost to Create: 4,500 gp, 360 XP, 9 days.