Quicksand

4th Level Transmutation

Any loose earth, mud, or sand in a 30ft square on the ground that you can see within range begins to churn and sink into itself, turning the area into difficult terrain for the duration.
When a creature enters the affected area for the first time on a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or take 3d6 bludgeoning damage and be restrained by the quicksand until the spell ends. A creature that starts its turn in the area and is already restrained by the quicksand takes 3d6 bludgeoning damage.
A creature restrained by the quicksand can use its action to make a Strength or Dexterity check (its choice) against your spell save DC. On a success, it frees itself.

Details

Author: Démos Tolmi 
Casting Time: 1 action
Range: 120ft
Components: V, S, M (A clump of mud or wet sand)
Duration: Concentration, up to 1 minute