To his astonishment, Khalil found the floor around him once again stable, as he willed himself to believe in a ground beneath his feat. To his dismay, however, he felt the air around him become extremely thin, and found he couldn't concentrate well enough to imagine both solid ground and a steady supply of air!
[sblock=Note]
Since it's a DC 15, an 11 is technically a failure, but I usually make a failure by 5 or less a "no, but..." kind of result.[/sblock]