Bhaal's Butchering Blades

You reach out your blooded hand and choose a target within range. Each target has blades strike invisibly from their back to their front, drawing their body upward with an otherworldly force. The victim takes 4d6 Piercing damage and continues to take 2d6 piercing damage per turn for as long as you maintain concentration. This spell also impedes the movement of its targets, forcing victims to move as if they were impeded by difficult terrain. At higher levels, this spell can target more than one entity. This spell inflicts bleeding once concentration has been broken.

On your later turns, you can take a Bonus action to recast the spell on a different target as long as you have not broken concentration.

Using a Higher-Level Spell Slot. The damage increases by 2d6, and the number of targets increases by 1 for each spell slot level above 3.