Corvaria’s Echoing Strike

When you cast this spell, you imbue your next melee weapon attack with resonating magical energy. The next time you hit a creature with a melee weapon attack before the spell ends, the attack unleashes a burst of concussive force that echoes within the target.

The initial attack deals its normal damage. At the start of the target's next turn, it takes $2d6$ thunder damage as the resonating energy intensifies. Additionally, if the target moves at least 10 feet before its next turn, it takes an additional $1d6$ thunder damage for every 10 feet moved beyond the first 10 feet, up to a maximum of $3d6$ extra damage.

At Higher Levels: The initial thunder damage increases by $1d6$ for each slot level above 2nd.