Ancient Deflection

When a creature succeeds on a damaging spell attack against you, you can use a reaction to make a Dexterity saving throw with a DC of 10 + the level of the spell to be deflected. On a failure, the attack counts as a critical hit. On a success, the spell is deflected directly back at the caster. The caster must make a Dexterity saving throw with disadvantage. On a success, they take the normal damage, and on a failure it counts as a critical hit.