Core:Temporary Hit Points

Temporary Hit Points (Temp HP) are not actual HP; they are a buffer against damage. When you have Temp HP and take damage, your Temp HP are reduced first, and any remaining damage carries over to your normal HP. If the type of damage is not one that would reduce HP (such as hack damage), then your Temp HP has no effect on the damage and is not reduced. You cannot spent Temp HP as an HP cost.