Tungsten Terrain

Tungsten spikes erupt from the ground, forcing all creatures within a 20-foot circle within range of the caster to make a Dexterity saving throw, on a failed save, a creature is knocked prone. The creature will take 2d6 piercing damage for every 5 feet whenever the creature moves into the area or within the area for every 5 feet wherever it has traveled. All creatures, excluding the caster, within this radius must spend 5 feet of movement for every 1 foot it moves.

On subsequent rounds, as a bonus action, you may force a creature within this terrain to make a Dexterity saving throw, on failed save that creature is knocked prone.