Blood Oath

You concentrate the flow of your own blood into a weapon of your choice, infusing it with necrotic strength. The next hit you make with your chosen weapon deals an extra 1d6 necrotic damage, as a burst of blood magic sears your enemy. Your weapon then loses this spell's effect.

The blood needed for this spell takes a toll on you, dealing 1d8 necrotic damage to yourself. 

This spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).