Spirit of the Blade

You charge your blade with spiritual energy, allowing it to cut through spirits and fiends with fearsome efficiency. The next Strike you make with a melee weapon or fist unarmed attack deals an additional 1d6 spirit damage. This bonus damage is lost if you don't attempt a Strike before the start of your next turn.

At 10th level, you deal an additional 2d6 spirit damage with this ability, and at 18th level, you deal an additional 3d6 spirit damage.