Black Tentacles

Duration: 1 minute, Concentration
Inky tentacles fill a 20 ft square on ground that
you can see, turning it into difficult terrain.When
a creature enters the area or starts its turn there,
it makes a Dex save or takes 3d6 bludgeoning
damage and is restrained on a failure. A creature
that starts its turn in the area and is already
restrained by the tentacles takes 3d6 bludgeoning
damage. A restrained creature can use its action to
free itself, making a Str or Dex