Dark Cloaked Dimension Slash

You channel darkness into a sword and, with a downward slash, releases that darkness which flies at the opponent. The slash is able to pierce the target hitting creatures or object behind it, the slash can also cut through large clouds of weave, and Defensive Magic (wall of force, Demiplane, Prismatic Wall, Shield) and even space itself. On a hit, the target takes 4d12 force damage This attack scores a critical hit if the number on the d20 is 18 or higher. On a critical hit, the blade deals an extra 8d12 force damage (for a total of 12d12 force damage).  The creature must roll DC 22 constitution saving throw, taking 20 (4d10) force damage gain 2 exhaustion points on a failed save, or half as much damage on a successful one (for a total of 12d12 and 4d10 force damage).