Cloak of Perun

When casting this spell you touch a willing creature and a protective magical force surrounds that creature, manifesting as a spectral cloak imbued with crackling lightning that covers them and their gear. The creature gains 10 temporary hit points for the duration. While the creatures has a pool of these temporary hit points, they gain an additional movement speed equal to 10ft. If a creature hits the creature with a melee attack while they have these hit points, the attacking creature takes 5 lightning damage.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the temporary hit points increase by 5 for each slot. When you cast this spell at 5th level or higher, attacks of opportunity made against you have disadvantage to hit, additionally your movement speed increases by 20ft instead of 10.