Vampiric Strike

As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell’s range, otherwise the spell fails. On a hit, the target suffers the attack’s normal effects, and an additional 1d4 necrotic damage. You gain temporary Hit Points equal to the damage dealt by the extra d4. The temporary Hit Points last one hour or until you successfully use this spell again at which time you may choose to keep the temporary Hit Points you already have or replace them with your new roll, the duration does not reset unless you take the new roll. 

This spell’s damage and temporary Hit Points increase when you reach higher levels. At 5th level, the bonus damage and temporary Hit Points increase to 2d4, at 11th level the bonus damage and temporary Hit Points increase to 3d4, at 17th level the bonus damage and temporary Hit Points increase to 4d4.