Klyndes

Light filtering through the haze of the plane of Steam casts shadows onto empty vapor, and sometimes those impossible shadows condense into a klyndes: a wisp of darkness living in the gaps between water and air. It speaks in a hiss of steam and learns no other language, so only magic allows conversation.

A flesh-eater, the klyndes hunts by sinking into a nebulous shadow state among the vapor motes. There it may move and watch, but it can neither affect nor be affected by physical things. It also seeps through the tiny gaps within all matter, so no ordinary wall holds it; magical barriers like wall of force do.

Shifting between solid and shadow takes a full round of rest in either direction. It nearly always ambushes, giving foes -2 on surprise, and lashes with four whiplike, blade-tipped limbs for 1d6 each. Since it is vulnerable while solid, it strikes only when confident of a meal.

Heat of any kind, magical or mundane, cannot hurt it in either form, and it needs no air. Water-affecting magic such as part water or water to dust strips its supporting vapor for 1d4 damage per three caster levels, in any form.

Each klyndes thinks itself unique, cannot be convinced otherwise and seems not even to perceive others of its kind, so no society exists or can. It rests deep in dark, damp steam, moving whenever other beings draw near, and spends half its time or more in a dreaming trance, the remainder hunting.

The plane's sole known predator, it mostly eats fabere, placid balloon-beasts that feed on steam, but gladly tries an exotic visitor. Since it is intelligent and open to reason, some outsiders have struck deals with klyndesi, who make excellent paid spies and assassins because their powers work off-plane. Dry air torments them, and a void like the plane of Vacuum kills them instantly. Cold-hearted alchemists say klyndes brain fluids are key to a potion that, like water breathing, lets the drinker breathe steam, fire or water.