Elemental Homunculus

Planar travel breeds clever fixes from odd sources. A circle of evil wizards from a secret society, preparing to venture into the Quasi-Plane of Ash, designed a homunculus that inhales ash and exhales clean air, letting a member who held it to the mouth breathe safely there. The secret soon leaked, and alchemists and other mages adapted it for breathing in all sorts of hostile places, especially on the Inner Planes.

Building on that work, another wizard devised a man-sized homunculus resembling an odd leather armor suit. Worn over the whole body, this skin passes its immunity to one element, chosen by its maker, to the wearer, but gives no other protection and does not count as armor. Both kinds are now fairly common and exist for almost every element. Breathers can even output substances besides air, so a fire creature with deep pockets could buy one that inhales air and exhales fire, and they can produce air from nothing where nothing exists to convert, as on the planes of Vacuum and of Positive and Negative Energy. Together they let beings of one element survive almost anywhere.

Neither kind can fight or even move; they are more like objects than creatures. Still, they can be wounded and killed by anything other than their keyed element, and a dead one protects no one. Breathers are therefore usually kept in a protective cage, either slung before the mouth on a harness or built into a helmet, for AC 8.

A skin covers its wearer and so takes damage before the wearer does, dying quickly in battle at its own AC 10. Worn beneath armor, it uses the armor's AC instead, and the wearer and skin split all damage evenly, so a 10-point hit costs each 5 hit points. It may still fail sooner than its owner would like, given the price, but far later than if worn on the outside. Armor worn over the skin gets no elemental protection and may be ruined. Sensible travelers avoid fights, and those depending on a skin are far keener to flee one.

Ordinary healing such as cure light wounds restores their hit points and their protective power, but potions are useless, since they have no mouths; a breather draws in one substance and releases another across its entire surface. Tales of hurt travelers spending their last healing magic on a damaged homunculus are common, because a dead skin halfway across the Elemental Plane of Fire is a far worse problem than a few more wounds.

As artificial creatures they are found in workshops, not lairs. Breathers fetch 100-500 gp from mages and alchemists, skins 300-1,000 gp, the price depending on circumstances, the element (more dangerous means pricier) and skill at haggling. In the great planar city, wizards and merchants often hawk them near portals to the Elemental Planes.

Elemental homunculi need no food or water, and breathers do not even need to breathe, doing so only when their element is present. They do not reproduce; only the correct procedures, materials and magic can produce one. Rumor says the ingredients include an elemental's essence, a mephit's flesh and blood from a genie, giant, dragon or similar being linked to the same element.