Source: Tal'Dorei Campaign Setting Reborn

You've learned secrets of hemocraft that grant you esoteric power at the price of your own life force. As a bonus action, you can choose to take 1d6 necrotic damage to gain a blood boon. Your blood boon lasts for 1 hour or until expended.

You can expend this blood boon to gain one of the following benefits:

• When you make an attack roll, you roll 1d6 and add it to the total.
• When you hit with an attack or spell, you deal an additional 2d6 necrotic damage.
• When you cause a creature to make a Strength, Dexterity, or Constitution saving throw, roll a d4 and reduce their save by the amount rolled.

The damage you take to gain a blood boon can’t be reduced in any way.