Essence Disruption

You tune into the innate energies holding someone together, causing a sudden and terrible snap in a crucial tether with the abrupt, ceremonial swipe of the crystal dagger. Choose a creature within range. They must make a Constitution saving throw. Regardless of whether or not they fail, they immediately lose half of their current hit points, as the life energy within them is siphoned out through the tear in their being.

If they fail the Constitution save, roll a 1d4. 1-2 is the left and right arm respectively, and 3-4 is the left and right leg respectively. The rolled limb is viciously (and quite painfully) dismembered from the body, as the energies keeping the body together explode violently to stop itself from completely deteriorating.