Enraged Vengeance

When an ally is downed (or killed) in combat, use your reaction to bolt directly at the cause. (15ft.) When you reach the enemy, roll a d4 (d6 if ally killed), and use Flurry of Blows that many times. This repeats until the enemy is dead, or until you are knocked out of it. When hit, roll a constitution saving throw with disadvantage (because you're leaving yourself wide open) and a difficulty class of 8. When cast at a higher level, you may not be downed or killed while the spell is in effect. When knocked out or spell finishes, roll 2 d4, the lower determining how many points of exhaustion are gained, the higher determining how many turns after the spell you have no action.