Cloudkill

This spell generates a billowing cloud of ghastly yellowish green vapors which is so toxic as to slay any creature with fewer than 4+1 hit dice, cause creatures with 4 + 1 to 5 + 1 hit dice to save vs. Poison at -4 on the dice roll, and creatures up to 6 hit dice (inclusive) to save vs. Poison normally or be slain by the cloud. 

The cloudkill moves away from the spell caster at 1” per round, rolling along the surface of the ground. A wind will cause it to alter course, but it will not move back towards its caster. A strong wind will break it up in 4 rounds, and a greater wind force prevents the use of the spell. Very thick vegetation will disperse the cloud in two rounds, i.e. moving through such vegetation for 2”. 

As the vapors are heavier than air, they will sink to the lowest level of the land, even pour down den or sinkhole openings; thus, it is ideal for slaying nests of giant ants, for example. (Volume of the cloud is 16,000 cubic feet or 16 10 ft. cubes.)

The caster is able to cast this spell so that it forms around him or her, if this is desired. However, any creatures staying within the cloud for more than one round, even though they have 7 or more hit dice/levels, will take 1d10 hit points of damage on the second and each succeeding round.