Burst Shield

A pale blue bubble of magical force appears and protects the target. Until the start of your next turn, they gain temporary hitpoints equal to 1d8 + your spellcasting ability modifier, including against the triggering attack. When a creature destroys the shield with a melee attack, it explodes, dealing force damage equal to the temporary hitpoints gained. 

When you cast this spell using a spell slot of 2nd level or higher, the temporary hit points increase by 1d8 for each slot.