Bloody Barrier

Your blood spills out around you, creating a volatile barrier that separates you and your assailant. immediately gain 3 Hit Dice worth of temporary hit points, Whenever your temporary hit points are reduced by an attack, you may deal damage equal to half your temporary hit points divided among creatures within 10 ft. of you. 

When you cast this spell using a spell slot of 2nd level or higher, the temporary hit points increase by 5 for each slot level above 1st.