Black Ribbons

You pull pieces of the plane of shadow into your own reality, causing a 20-foot cube to fill with inky ribbons that turn the area into difficult terrain and wrap around nearby creatures. Any creature that ends its turn in the area becomes restrained by the ribbons until the end of its next turn, unless it makes a successful Dexterity saving throw. Once a creature succeeds on this saving throw, it can’t be restrained again by the ribbons, but it’s still affected by the difficult terrain.