Thickening fog

You choose a spot in range, you open your hands facing down and slowly raises your hands, from the chosen spot a thick mist emerges from the ground.
The mist spreads around corners and crevasses.
For the duration, all creatures in the fog are heavily obscured, any attacks on them or from them are with 1 disadvantage.
(A 20 miles per hour gust of wind or a Grade 3 wind spells can disperse the fog.)