delayed aftershock

: (n) a sword technique that requires the user to slash an object, which will inflict interior damage while keeping the exterior unblemished; a master of this technique can sculpt the interior to their liking.

After Wa De Kun used delayed aftershock on a boulder, the boulder seemed to remain unchanged. However, when you look inside the boulder via an x-ray, you can see a replica of Michelangelo's David.