How often and how long can a Dust Quasi use this attack? The original text does not say.
Come to think of it, we have the Air Elemental's "The elemental can transform itself into a whirlwind once every 10 minutes and remain in that form for up to 1 round for every 2 HD it has" so might as well use that for the duration.
Okay, I fancy roughing out a Dust Storm special attack.
How's this:
Dust Storm (Su): A dust quasi-elemental can transform itself into a whirlwind once every 10 minutes and remain in that form for up to 1 round for every 2 HD it has. In this form, the elemental can move along a surface or fly (perfect maneuverability) at its land speed.
The dust storm can be up to 30 feet tall and up to 80 feet in diameter, depending on the elemental's size. The dust quasi-elemental controls the exact dimensions, but it must be at least 10 feet tall and 10 feet in diameter.
The elemental's movement while in dust storm form does not provoke attacks of opportunity, even if the elemental enters the space another creature occupies. Any creature or object that makes contact with the dust storm must succeed at a Reflex save or be blinded for X rounds. It must also succeed on a Fortitude save or take the indicated damage. The save DCs are Constitution-based.
The dust storm creates a swirling cloud of debris centered on the elemental. The cloud obscures all vision, including darkvision, beyond 5 feet. Creatures 5 feet away have concealment, while those farther away have total concealment.
Creatures caught in the dust storm can otherwise act normally, but must succeed on a Concentration check (DC 15 + spell level) to cast a spell. Creatures caught in the dust storm take a -4 penalty to Dexterity and a -2 penalty on attack rolls. The elemental can have as many creatures inside the dust storm as will fit inside its volume.
[TABLE="width: 500"] [TR] [TD]
Elemental
[/TD] [TD="align: center"]
Height[/TD] [TD="align: center"]
Weight[/TD] [TD="align: center"]
Blindness
Save DC[/TD] [TD="align: center"]
Damage
(Save DC)
[/TD] [TD="align: center"]
Diameter[/TD] [/TR] [TR] [TD]Small[/TD] [TD="align: center"]4 ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]1d6 (DC)[/TD] [TD="align: center"]10-20 ft.[/TD] [/TR] [TR] [TD]Medium[/TD] [TD="align: center"]8 ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]2d4 (DC)[/TD] [TD="align: center"]10-30 ft.[/TD] [/TR] [TR] [TD]Large[/TD] [TD="align: center"]16 ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]3d4 (DC)[/TD] [TD="align: center"]10-40 ft.[/TD] [/TR] [TR] [TD]Huge[/TD] [TD="align: center"]32 ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]4d4 (DC)[/TD] [TD="align: center"]10-50 ft.[/TD] [/TR] [TR] [TD]Greater[/TD] [TD="align: center"]36 ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]4d4 (DC)[/TD] [TD="align: center"]10-60 ft.[/TD] [/TR] [TR] [TD]Elder[/TD] [TD="align: center"]40 ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]4d4 (DC)[/TD] [TD="align: center"]10-60 ft.[/TD] [/TR] [TR] [TD]Monolith[/TD] [TD="align: center"]?? ft.[/TD] [TD="align: center"]X lb.[/TD] [TD="align: center"]XX[/TD] [TD="align: center"]6d4 (DC)[/TD] [TD="align: center"]10-80 ft.[/TD] [/TR] [/TABLE]