Shadow Tentacles

4th level - Elemental (shadow) or Spiritual (invocation or umbramancy)

Casting Time: 1 action
Range: 90 feet
Components: V, S, M (a giant octopus' or squid's tentacle piece)
Duration: Concentration, up to 1 minute

Shadowy, writhing tentacles fill 20 square feet of the ground within your line of sight, within the spell’s range. For the duration of the spell, these tentacles transform the ground in the area into difficult terrain.

When a creature enters the affected area for the first time during its turn, or begins its turn there, it must succeed on a Dexterity saving throw or take 3d6 bludgeoning damage and be restrained by the tentacles until the spell ends. A creature that begins its turn within the area and is already restrained by the tentacles takes 3d6 bludgeoning damage.

A creature held by the tentacles may use its action to make a Strength or Dexterity check (as it chooses) against the DC to resist magic. On a success, it breaks free.