Create fog

As you cast this spell, fog rises from the ground in an area around you. The fog reduces (dark)vision by a third, rounded up; this decrease in range also applies for light sources and the sun's light never gives more light than dim light, as long as the fog is there.
If cast outside, the fog doesn't reach into buildings or caves. The shape of the affected area is chosen by you at the moment of casting the spell, the range is a circle with a radius of 2 miles.
If you concentrate on the spell for the full duration, the effect becomes permanent. The water and the diamond get consumed by the spell like usually, but the water skin fuses with the ground. An antimagic field or disintegrate spell, as well as getting rid of the waterskin by burning it or destroying it with acid, makes the fog disappear slowly during an hour. However, hitting it with any non-magical weapon, doesn't have any effect.