Control vapor was a divine magic spell available to druids and specialty priests of Eldath, the Mother of the Waters. It gave the caster command of the movement rate and direction of magical and non-magical smokes, vapors, clouds, and mists, including creatures in gaseous form. A less powerful arcane version was known but rare among the wizarding community.
This spell could be cast at a point up to 120 ft (37 m) away and affected a spherical volume with a radius of 90 ft (27 m) centered on that point. Within this sphere, for the next nine minutes, the caster could designate the speed (from zero to a radius-length per minute) and direction of any vapors caught in the sphere, regardless of prevailing winds or air currents (natural or magical). Higher level casters could increase the radius and duration of this spell. The arcane version affected an area of 30 ft (9 m) diameter only. It could, however, additionally be used to clense this sphere of all vapors.
Examples of vapors that could be controlled included fog, mist, smoke, cloudkill, fog cloud, incendiary cloud, smoke ghost, the smoke from pyrotechnics, and gaseous breath weapons. The caster could hold, reshape, split, or combine vapors as desired. Control vapor could also be used to control or capture creatures in gaseous form, such as vampires, air elementals, and those using wind walk. These creatures had no chance to resist the magic of this spell, but could transform to a different form (such as becoming corporeal) at half their normal rate, if they had the ability to do so. For the arcane version, gaseous creatures did have a chance of resisting the spell.
This spell had no effect on swarms of insects or other nongaseous creatures, but smoke could be manipulated to intersect an insect plague, for example. Any vapor that passed out of the stationary sphere where this spell was operating became free of the caster's control.