True Counterspell

You make a circular motion with your hands, producing an arcane mirror only you can see. You attempt to reflect the effects of a spell cast by a creature that you can see within range.

If the creature is casting a spell of 5th level or lower, roll a d20. If you roll a natural 15 or greater, the effects of the spell are reflected back at the spell caster, and they take any damage or suffer any effects as if you were the caster. When you reflect the spell, use your spell attack or your spell save DC. Any charm effects that allow you to command a creature last for a maximum of one minute only.

If you roll a natural 14 or lower, the spell is negated as per a normal Counterspell. 

If the target spell is of 6th level or higher, make an ability check using your spellcasting ability. As per a regular Counterspell (PHB 228), the DC is 10 + the spell’s level to Counterspell normally. To successfully True Counterspell and reflect a spell above the 5th level, the DC is 12 + the spell’s level, with a natural 20 being the only means to bounce back 8th and 9th level spells.

You may add your spellcasting ability to normally Counterspell, but to True Counterspell you must only use natural rolls on the d20.

On a successful True Counterspell, you will be unable to cast this spell for 1d4 rounds. If you fail to reflect the targeted spell, you will be unable to take a reaction during the next round, even if you managed to Counterspell normally using this spell.

At Higher Levels. When you cast this spell at 6th level or higher, as per normal Counterspell, the interrupted spell has no effect if its level is less than or equal to the level of the spell slot you used. 

Additionally, the DC to True Counterspell and reflect a spell decreases by 1 for each spell slot you spend above the 5th. 

On a success, if the countered spell causes damage, add an extra 2d6 damage for each spell slot above the 5th that you used to cast True Counterspell. The damage type is that of the countered spell.