Arcane Quicksand

An area of quicksand appears in a radius of 10 ft. Any creature that moves through the sand does so at half speed. A creature that ends it’s turn in the sand beings to sink in the sand, reducing it’s speed to 0 until it makes a strength saving throw or aided by a creature that makes a similar check (against casters save DC). All attacks against sinking creatures have advantage. Sinking creatures have disadvantage on Dexterity saving throws.