Creeping Darkness

You fill a 30 ft diameter, 10 ft tall cylinder with inky black darkness.  At the start of each turn, the magical darkness spreads 20 ft in a direction of your choice, seeping through even the tiniest of holes and gaps.  Any creature in the cloud can not see, even if they have dark-vision nor can they hear or speak as the cloud mutes all sound as well, preventing any spellcasting with the vocal component.  All non magical light is extinguished with in and magical light from a spell 4th level or lower is suppressed with in the cloud.

A strong consistent wind over 20 miles per hour can disperse the cloud after 1 round of exposure.