Agonizing Wound

Covering your weapon in dark grey energy, you make a melee attack with the normal effects of the weapon. The weapon's energy seeps into the creature's wound on a hit, causing immense pain. The creature must make a Strength-saving throw; on a failure, the creature takes 1d6 necrotic damage, causing the creature to be unable to concentrate on any spells or abilities as the pain becomes unbearable and the spell has no effect on a success. The spell ends after one minute or if the creature succeeds on the saving throw. 

The spell's damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).