You create a field of elemental energy fire, ice, lightning, acid you can choose when you cast the spell in a 15 FT radius around you if a target enters this field or starts its turn in the affected area it takes 5d8 of the respective damage type and it must make a dexterity saving throw taking 2d8 on a failed save and get pushed out of the bubble on a successful save it takes half damage from your spell and doesn't take the 2d8 damage  the field is a bubble and is opaque