Black Ribbons

You pull pieces of the Shadow Realm 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 shadow ribbons until the end of its next turn unless it makes a successful Dexterity saving throw. Once a creature makes this saving throw successfully, it can’t be restrained again by these black ribbons, but it’s still affected by the difficult terrain.