Elemental Spellshield

You attempt to harness the powers of the elements to shield yourself. If another creature is casting a spell of 3rd level or lower at you, its spell is absorbed into the shield and has no effect. If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect. On a fail, the spell effects you as normal. Spells successfully absorbed by the shield can be transmitted to an elemental spell of an equal level to the spell absorbed, which can include upcasted spells. The element is decided when the spell is first cast and can be any of the following; acid, cold, fire, lightning, or thunder. This spell can be discharged from the shield as an action, using the caster's spell attack. While the shield is up, anything within 5 feet of you takes 2d6 damage of the corresponding elemental type at the beginning of their turn. The shield also grants the caster resistance to that elemental type for the duration. 

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the interrupted spell has no effect if its level is less than or equal to the level of the spell slot you used, as well as the 2d6 damage being increased by 1d6 per increased level.