Necklace of adaptation

A necklace of adaptation was a magical necklace that protected the wearer from things that affected their ability to breathe.

Description
It took the form of a platinum medallion hanging on a heavy chain.

Powers
The necklace enclosed the wearer in a shell of fresh air, allowing him or her to always be able to breathe, even when underwater or in a vacuum. This in turn made the wearer immune to all harmful gases and vapors, such as inhaled poisons and magical effects like stinking cloud or cloudkill.

Creation
Crafting one required an alter self spell.

Other Versions
Monadic devas could naturally breathe in any environment as if they wore a necklace of adaptation.