Carpet of Shadow

You move your hands across the ground as if rollout a carpet. A 20ft² square pool of tar appears, centered on a point within range. If the spell affects a space a creature occupies, the spell fails. The pool is 10ft deep. When a creature enters the area, it must pass a Strength save or sink 2ft into the pool and become restrained. At the start of each creature's turns, it sinks another 2ft. It can escape by making another Strength check against your spell save DC if it's not fully submerged. A creature that's completely covered is blinded and can't breathe.

A creature can pull another out of the pool by using its action to make a Strength check against your spell save DC. If the spell ends while a creature's in the pool, it rises to the surface, appearing prone on the floor in the same space it occupied in the pool.

At Higher Levels. When cast using a slot of 6th, the duration increases to 10 minutes, 1 hour when cast at 7th level, 8 hours when cast at 8th level, or until dispelled if cast at 9th level. Also, the spell doesn't require concentration when cast at 7th or higher.