Blood Ward

Boss Feat: This feat is not balanced for player characters, and cannot be obtained through normal level progression. Boss feats are intended for DMs to balance their characters to make boss fights more challenging and raise powerful characters above the levels of normal play.

As a bonus action, you can cast Counterspell with no components or spell slots. When casting it in this way, you may upcast it to a level equal to your proficiency bonus. You then lose hit points equal to ten times the level it was cast at. You can use this ability once per long rest.