Miasma

Masters of the Wild: A Guidebook to Barbarians, Druids, and Rangers (MW)Updated Supplementals (3.0)

Miasma is a D&D 3.5 spell (Evocation) from MW. On class lists for Druid (Level 4), Druid Variant (Level 4), Druidic Avenger (Level 4). Range or area: Medium (100 ft. + 10 ft./level); Saving throw: See text; Duration: 5 rounds/level; Casting time: 1 standard action.

School
Evocation
Casting Time
1 standard action
Components
V, S, DF
Range
Medium (100 ft. + 10 ft./level)
Target
One living creature
Duration
5 rounds/level
Saving Throw
See text
Spell Resistance
Yes

By filling the subject’s mouth and throat with unbreathable gas, you prevent him or her from doing much more than coughing and spitting.
The subject can hold his or her breath for 2 rounds per point of Constitution but must make a Constitution check (DC 10 +1 per previous success) each round thereafter to continue doing so.
Failure on any such check (or voluntary resumption of breathing) causes the subject to fall unconscious (0 hp).
On the next round, the subject drops to -1 hit points and is dying; on the third round, he or she suffocates (see Suffocation in Chapter 3 of the DUNGEON MASTER‘S Guide).