Thunder Cloak

The caster touches someone creating a cowl of lightning over them. For the duration of the spell the affected creature has double movement speed, an extra reaction and deals an extra 1d6 lightning damage on any melee attack. Once the spell wares off or is dispelled the creature takes 2d6 lightning damage and gains one level of exhaustion. 

Damage increases by 1d6 for every additional spell level.

Creatures immune to lightning damage cannot be affected by the spell.

Creatures resistant to lightning damage gain an additional half movement speed, no additional reaction and only deal an extra 1d4 lightning damage.