Blood Diablist

As a bonus action ignite your blood and declare your enemy. For 1 minute you gain your proficiency bonus to both hit and to damage. In return, once per round on your action you take your proficiency bonus in damage. This effect ends when either 1 minute has passed or the declared enemy dies. If the declared enemy dies in the 1 minute timespan, you can spend a number of hit dice equal to your tier.

You can use this once per long rest.