Squirming black tentacles fill a 20-foot square on the ground (Concentration, 1 min). The area is Difficult Terrain. Each creature in the area when cast, and each creature that enters it, makes a STR save. On a failure: takes 3d6 Bludgeoning damage and has the Restrained condition. A Restrained creature takes 3d6 Bludgeoning damage at the start of each of its turns. It can use its Action to make a STR or DEX check vs. your spell save DC to escape.

Material: a piece of tentacle from a giant octopus or giant squid