Warlock's Sacrafice

In order to regain one spell slot of X level, you take Xd4 necrotic damage (for example, for a 3rd level spell slot you would take 3d4 damage). Any healing you receive for the next hour is reduced by the total damage taken this way, including by taking a short or long rest.

For spell slots above level 6, take Xd4 + X necrotic damage (for a level 6 spell slot, take 6d4 + 6).